Report on the U.S. Program for the International Geophysical Year: July 1, 1957 - December 31, 1958 (1965)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

I l l GEOMAGNETISM PROGRAM Askania E a r t h Variograph

GEOMAGNETISM PROGRAM Page A. Organization of Technical Panel on Geomagnetism 127 B. Summary of Panel Actions 127 C. Project Objectives and Results 129 3.1 Geomagnetism Headquarters, Data Reduction & P u b l i c a t i o n 130 3.2, 3.13, 3.14 - Operations of Magnetic Observatories I n the A n t a r c t i c 131 3.3 Guam - Koror Magnetic Observatories 132 3.4 East-West Network of Magnetic Recording Stations 133 3.5 North-South Network (Alaska) of Magnetic Recording Stations. . . . 134 3.6, 3.7 - Magnetic Gradient Studies I n Alaska 135 3.8 Operations of Rapid-Run A u x i l i a r y Magnetographs 136 3.9 Single Component V i s i b l e Recording Magnetographs 136 3.10 Sub-Audio-Frequency Geomagnetic Fluctuations 137 3.11 Magnetic Observations a t J a r v l s , Palmyra and Fanning 140 3.12, 3.15, 3.17 - Equipment f o r Magnetic Stations a t J a r v l s , Palmyra, Fanning, A r c t i c Ice Floe ( S t a t i o n A ) , and the South American 5-Statlon Network 141 3.16 Equatorial E l e c t r o j e t i n Peru 142 126

I l l , GEOMAGNETISM PROGRAM A. Organization of Technical Panel on Geomagnetism 1, Establishment of Panel. L e t t e r s were w r i t t e n i n December 1954 - January 1955 t o nominees f o r panel membership, M, A, Txive was asked t o convene the f i r s t meeting, a t which E. 0, Hulburt was elected Chairman, and E, B, Roberts, Secretary. The panel recommended t h a t R. R, Revelle be I n v i t e d t o become a member i n order to e f f e c t l i a i - son w i t h the panel on oceanography. Chairman. L a t e r , E, B, Roberts was designated as Vlce- 2, Composition of the Panel. ( A f f i l i a t i o n a t time of appointment.) a. Panel Miembers Leroy R. Alldredge Walter M. Elsasser Edward 0, Hulbnrt Roger R, Revelle E l l i o t t B. Roberts Merle A. Tuve V i c t o r Vacquier E. H. Vestlne Naval Ordnance Laboratory U n i v e r s i t y of Utah Chairman - r e t i r e d ( D i r e c t o r S c i e n t i f i c Research, NRL) Scripps I n s t i t u t i o n of Oceanography Vice-chairman: U. S, Coast and Geodetic Survey Carnegie I n s t i t u t i o n of Washington, De- partment of T e r r e s t r i a l Magnetism New Mexico I n s t i t u t e of Mining and Tech- nology Carnegie I n s t i t u t i o n of Washington, De- partment of T e r r e s t r i a l Magnetism b. Consultants Walter S. McAffee, J r . John McClay A. G. McNlsh J. H. Nelson U. S. Army Signal Research and Development Laboratory Geophysics Research Center (AFCRC) National Bureau of Standards U. S. Coast and Geodetic Survey c. Secr e t a r i a t (IGY S t a f f ) G. F. S c h i l l i n g ( t o May 1955) Stanley Ruttenberg (from May 1955) 3. Panel Meetings. Four meetings of the panel were held i n the period 1955-1956. F i r s t Meeting Second Meeting T h i r d Meeting Fourth Meeting January 24, 1955 February 14, 1955 May 5, 1955 May 15, 1956 Washington, D. C. Washington, D. C. Washington, D. C. Washington, D. C, B, Summary of Panel Actions 1, Working Groups. A group was appointed (Drs. Vacquier, Vestlne, McNlsh) t o study the p o s s i b i l i t y of budgeting f o r a program of analysis and research on IGY data i n geomagnetism, p a r t i c u l a r l y w i t h reference t o i n t e r d i s c i p l i n a r y problems. E. H. Vestlne and J. H. Nelson were asked to study the question of chains of 127

GEOMAGNETISM sta t i o n s I n western United States and Alaska, and of special observations i n Alaska to o b t ain gradients. 2. O r i g i n a l Program. Following CSAGI recommendations, a program o f determining f i n e s t r u c t u r e of t r a n s i e n t phenomena was planned I n Alaska, where two s t a t i o n s would be established about 100 miles from College to form a t r i p a r t i t e network, A d i f f e r e n - t i a l magnetograph was being designed f o r i n s t a l l a t i o n a t College; the 5-10 mile spac- ing between elements was expected t o give Information on magnetic f i e l d g r a d i e n t s , p a r t i c u l a r l y during magnetic storms. Rapid-run Instrtiments were t o be I n s t a l l e d a t a number of s t a t i o n s t o study the higher frequency f l u c t u a t i o n s . Two s t a t i o n s were planned i n the A n t a r c t i c and several locations i n the P a c i f i c near the magnetic equa- t o r were suggested as possible s i t e s f o r new observatories. 3. A n t a r c t i c Program. As plans f o r the U. S. program enlarged, i t was decided t o i n s t a l l several new st a t i o n s I n the A n t a r c t i c . The Panel studied the equipment needs f o r these s t a t i o n s and came to the conclusion t h a t i t was not necessary t o have abso- l u t e measurements a t a l l s t a t i o n s a t a l e v e l t h a t would be considered necessary f o r permanent-type s t a t i o n s . The savings thus e f f e c t e d could be used t o strengthen the study of the f l u c t x i a t l o n s and t r a n s i e n t phenomena. Later I n the planning phase i t was decided t h a t i t might be very desirable t o i n s t i t u t e a new program i n South Amer- ica (see discussion below). I n order t o f i n d funds t o meet the expense of t h i s pro- gram i t was decided t o eli m i n a t e magnetic measurements from one of the a n t a r c t i c s t a - t i o n s . I t was ascertained from the B r i t i s h IGY Committee t h a t magnetic measurements were t o be included i n the program a t the B r i t i s h s t a t i o n a t Halley Bay, which would only be one hundred miles from the proposed U. S. s t a t i o n a t the Weddell Sea ( E l l s - w o r t h ) . I t was there f o r e decided t o recommend t h a t the magnetic program be cancelled a t E l l s w o r t h . 4. Close Spaced Chains of Stations. Early i n the program i t was recognized t h a t obser- vations from a chain of st a t i o n s might provide valuable information on magnetic storm phenomena. Pre?.imlnary budgetary considerations, however, precluded the planning of such s t a t i o n s . As the budget was Increased f o r the U. S. program, i t was then found possible t o include such experiments. The working group, c o n s i s t i n g o f Dr. E. H. Vestlne and Mr. J. H. Nelson, studied the p o s s i b i l i t i e s of such experiments and rec- ommended t h a t two chains of s t a t i o n s be planned. a. North-South Chain i n Alaska. Five locations were recommended i n Alaska; each s t a t i o n would have a three-component Askanla Varlograph i n s t a l l e d i n a pref a b r i c a t e d nonmagnetic s h e l t e r and serviced from the main observatory a t College. b. Western United States. I n order t o study the morphology of m i d - l a t i t u d e of geomagnetic disturbances, i t was recommended t h a t an east-west chain of s t a t i o n s be operated i n Western United States w i t h spacing of approximately 300 kil o m e t e r s . Five locations were selected where normal s e n s i t i v i t y Askania Variographs could be I n s t a l l e d i n p r e f a b r i c a t e d nonmagnetic s h e l t e r s . Two other s t a t i o n s were selected t o give a short north-south cross arm. 5. P a c i f i c Program. Early planning c a l l e d f o r s t a t i o n s near the magnetic d i p equa- t o r i n the Eastern and Western P a c i f i c . A f t e r plans of other nations were ascertained and i n conjunction w i t h other U. S. programs, p a r t i c u l a r l y oceanography, i t was de- cided t o organize a t h r e e - s t a t i o n network of s t a t i o n s i n the Line Islands i n the East- ern P a c i f i c t o be undertaken by the Scripps I n s t i t u t i o n of Oceanography, U n i v e r s i t y of C a l i f o r n i a , I t was also f i n a l l y decided t o i n s t a l l two s t a t i o n s a t Goam and Koror i n the Western P a c i f i c , 6. A r c t i c Program, When plans were developed by the U, S, National Committee f o r s c i e n t i f i c s t a t i o n s i n the A r c t i c Basin, e i t h e r on a f l o a t i n g i c e i s l a n d (7-3) or a s t a t i o n on the pack i c e , i t was decided t h a t one of these s t a t i o n s might be a u s e f u l 128

GEOMAGNETISM l o c a t i o n f o r a magnetograph. I t was decided t o put the magnetograph a t S t a t i o n A, which would be located several hundred miles n o r t h of Barrow, Alaska, on the pack I c e . Absolute measurements were not provided f o r Inasmxich as t h i s s t a t i o n would not remain f i x e d but would d r i f t and r o t a t e under the movement of the pack i c e , 7, High Frequency Geomagnetic Studies. There were suggestions I n the e a r l y phases of the planning t o extend the frequency range of studying t r a n s i e n t phenomena t o d i s - turbances w i t h periods of one second to a few hundredths of a second, i n other words. I n the subaudlo frequency range. Dr. Leroy Alldredge and Elwood Maple prepared a pro- posal f o r the Panel. Discussions were also held w i t h other I n t e r e s t e d i n v e s t i g a t o r s such as R. E. Holzer, I n s t i t u t e of Physics, U n i v e r s i t y of C a l i f o r n i a , Los Angeles, and a proposal was also examined from Dr. A. R. Jordan, Denver Research I n s t i t u t e , U n i v e r s i t y of Denver. I t was f i n a l l y decided t h a t a program undertaken by the Geo- physics Research D i r e c t o r a t e under the supervision of Elwood Maple i n cooperation w i t h the Denver Research I n s t i t u t e would be recommended. Dr. Holzer having withdrawn h i s proposal i n view of other commitments. This program would con s i s t of f i v e s t a t i o n s a t various magnetic l a t i t u d e s w i t h slow-speed tape recorders, s p e c i a l l y designed low- noise a m p l i f i e r s and oriented magnetic c o l l s as sensing elements. 8, V i s u a l Recording Program. The Geomagnetism Panel was asked by the Technical Panel on Ionospheric Physics t o look i n t o the f e a s i b i l i t y of providing some d i r e c t reading magnetometers f o r p a t r o l purposes a t selected ionospheric s t a t i o n s . Several types of equipment were t e s t e d , i n c l u d i n g a commercially a v a i l a b l e vacuum tube s e n s i t i v e to ambient magnetic f i e l d s . The Coast and Geodetic Survey f i n a l l y made recommendations as to the most s u i t a b l e types of instruments and, under a p r o j e c t approved by the Panel, furnished them f o r operation a t locations selected by the Ionospheric Physics Panel. 9, Data Reduction and P u b l i c a t i o n . I n response t o CSAGI recommendations developed a t the Rome meeting, the Panel discussed the needs f o r various types of data reduction and the exchange of data i n the geomagnetism program. Several schemes f o r the p u b l i - c a t i o n of selected data from the geomagnetic s t a t i o n s were also discussed. The Panel accepted the r e p o r t of the Coast and Geodetic Survey on the f e a s i b i l i t y of publishing magnetograms and hourly values as s t a t i o n books i n the number of about 500 copies f o r the U. S. s t a t i o n s . A t the time o f t h i s Panel a c t i o n , the number of U. S. s t a t i o n s was 8; l a t e r btidgetary expansion of the program approximately doubled the number of st a t i o n s and i t proved t o be possible t o give complete p o b l l c a t i o n t o only a selected number of s t a t i o n s . P t i b l i c a t l o n of l i m i t e d Information was then planned f o r the r e - maining s t a t i o n s . C. Proje c t Objectives and Results 1. Summary of Program. The geomagnetic program consisted of a series of experiments mainly designed t o y i e l d f a c t s about the magnetic f i e l d f l u c t u a t i o n s which a r i s e from influences e x t e r n a l t o the surface of the e a r t h . Projects provided f o r the procure- ment, i n s t a l l a t i o n and operation of geomagnetic equipment i n several new st a t i o n s and f o r the operation, c o l l e c t i o n and analysis of data from new and e x i s t i n g geomagnetic s t a t i o n s . 2. Order of Protect D e s c r i p t i o n . The pr o j e c t s t h a t are described i n the f o l l o w i n g pages are i n numerical order t o correspond w i t h the o r i g i n a l f ormulation of the pro- gram, w i t h the exception t h a t a few c l o s e l y r e l a t e d p r o j e c t s are grouped together. 129

GEOMAGNETISM Project 3,1 - Geomagnetism Headquarters, Data Reduction and P u b l i c a t i o n 1. Objectives. a. F i e l d Operations. This p r o j e c t , a t the U. S. Coast and Geodetic Survey, provided f o r the operations headquarters f o r a l l of the geomagnetism p r o j e c t s under- taken by the Coast and Geodetic Survey f o r the IGY. U t i l i z i n g the f a c i l i t i e s of the Fredericksburg Magnetic Observatory, instruments were t e s t e d , c a l i b r a t e d and stan- dardized. I n a d d i t i o n , observers f o r the new st a t i o n s were t r a i n e d f o r the operation and maintenance of instruments. S t a f f members of the Geomagnetism Branch, Geophysics D i v i s i o n , USCGS, assisted i n i n s t a l l a t i o n of instruments a t new locations and made v i s i t s during the course of the IGY to many s t a t i o n s i n order to assure u n i f o r m i t y of techniques and to a s s i s t i n solving problems a r i s i n g w i t h f i e l d operations, b. Data Reduction and P u b l i c a t i o n , The Survey supervised the reduc t i o n of mag- netograms taken during the IGY which consisted of ( i ) the sc a l i n g of mean hou r l y or- dinates of the three vector components recorded on standard magnetograms, ( i i ) con- v e r t i n g the ordinates to gammas (or minutes of arc) by a p p l i c a t i o n of scale-value fac- t o r s , and ( i i i ) the a d d i t i o n of base-line values, where possible, to the hourly values to y i e l d tables of absolute hourly means. Steps ( i i ) and ( i i i ) required a s u b s t a n t i a l amount of study and analysis of the records from each s t a t i o n t o insure the adoption of the most s a t i s f a c t o r y scale values and base l i n e s . 2. Operations. Data from 7 IGY observatories ( L i t t l e America, Byrd, Wilkes, Koror, Guam, Healy, Big Delta) have been published i n booklet form patterned a f t e r the reg- u l a r observatory p u b l i c a t i o n s of the Coast and Geodetic Survey. These books include tables of hourly-values and reproductions of a l l normal-speed n o r m a l - s e n s i t i v i t y mag- netograms. Four a d d i t i o n a l IGY recording s t a t i o n s ( J a r v i s I s l a n d , Fanning I s l a n d , B e l o i t , Anchorage) were treated by p u b l i c a t i o n of hourly-value tables but without reproductions of magnetograms. Some processing of hourly-value tables was done f o r eleven more recording s t a t i o n s (Barter I s l a n d , Kotzebue, For t Yukon, Northway, H a l l e t t , P r i c e , Casper, L e a d v i l l e , Espanola, B u r l i n g t o n , C a r r o l l t o n ) but w i t h o u t p u b l i c a t i o n , the r e s u l t s are a v a i l a b l e on m i c r o f i l m f o r workers who req u i r e these data. The book- l e t s were p r i n t e d i n l i m i t e d q u a n t i t y and d i s t r i b u t e d n a t i o n a l l y and i n t e r n a t i o n a l l y t o research organizations and s c i e n t i s t s known to be i n t e r e s t e d , and have been sub- mit t e d also to the World Data Centers, For data not published microfilms were sup- p l i e d to the World Data Centers, 3, Personnel, The general program of the Coast and Geodetic Survey was under the supervision of E. B, Roberts, Chief, Geophysics D i v i s i o n , and J. H. Nelson, Chief, Geomagnetism Branch, Mr, Joel B, Campbell served as the Survey's IGY operations o f f i c e r . The processing of data was under the supervision of Kendall Svendsen and John Gettemy, 130

GEOMAGNETISM Projects 3.2, 3.13 and 3.14 - Operation of Magnetic Observatories i n the A n t a r c t i c 1. Objectives, These pro j e c t s of the U. S, Coast and Geodetic Survey provided f o r i n s t a l l a t i o n of standard magnetic observatories a t U. S. sta t i o n s i n the A n t a r c t i c and f o r operation of t h i s equipment during the IGY, I n a d d i t i o n t o the a c q u i s i t i o n of data f o r the purposes of studying phenomena of the magnetic f i e l d i t s e l f , i . e . , the absolute value of the f i e l d and i t s changes and magnetic storms, these p r o j e c t s were part of a broad program i n v o l v i n g the c o r r e l a t i o n of data from many d i s c i p l i n e s , i n c l u d i n g ionospheric physics, aurora and cosmic rays. 2. Operations. Equipment was I n s t a l l e d a t L i t t l e America, Byrd S t a t i o n , Amundsen- Scott (South Pole) S t a t i o n , Wilkes S t a t i o n , and, i n cooperation w i t h New Zealand, Cape H a l l e t t S t a t i o n . New Zealand s c i e n t i s t s operated the equipment a t Cape H a l l e t t and U. S. observers are responsible f o r operations a t the other A n t a r c t i c Stations, The Instrumentation a t L i t t l e America, Byrd and Wilkes Stations was tha t of a standard magnetic observatory, w i t h normal-speed and rapid-run records of the vector changes of the f i e l d , and w i t h regular absolute c a l i b r a t i o n s f o r c o n t r o l of variometer performance and f o r determination of secular change. Equipment a t Cape H a l l e t t and at the Pole S t a t i o n consisted of a 3-component Askania Variograph, 3. Personnel, This p r o j e c t was under the general supervision of E, B, Roberts, J, H. Nelson and Joel B. Campbell, 4. Data, Data have been processed and published according to CSAGI recommendations as discussed under Project 3,1, A l l IGY A n t a r c t i c data have been submitted to the data centers, 5. Results. As these were p r i n c i p a l l y data c o l l e c t i n g p r o j e c t s , r e s u l t s are d i s - cussed elsewhere (Projects 22.13 and 50.1), 131

GEOMAGNETISM Project 3,3 - Guam - Koror Magnetic Observatories 1, Objectives, Numerous scattered observations over a period of a number of years had i n d i c a t e d a region near the magnetic d i p equator of s p e c i a l geomagnetic s i g n i f i - cance — the locus of the postulated " e q u a t o r i a l e l e c t r o j e t . " Questions had a r i s e n , moreover, as to the r e l a t i o n s between the e l e c t r o j e t and the geographic equator, the geomagnetic equator, and the magnetic dip equator, Koror was chosen by the U. S. Coast and Geodetic Survey as one of the nearest possible s i t e s t o the d i p equator. (Later f i e l d measurements near the Koror observatory Indicated the o b j e c t i v e of loca- t i o n had been achieved w i t h remarkable accuracy, f o r the p o s i t i o n of the equator i t - s e l f was found t o be probably less than ten miles from the observatory,) A t t h i s p o i n t there was appreciable separation of the three "equators," the geographic l a t i - tude of the s t a t i o n being 7° 20' North, and the geomagnetic l a t i t u d e 3.2° South. The s i t e a t Guam was chosen as a c o n t r o l s t a t i o n f o r Koror, being f a r enough away t o res- pond very l i t t l e t o the e f f e c t s of the e l e c t r o j e t . 2, Operations. Prefabricated non-magnetic aluminum b u i l d i n g s were erected f o r the recording instruments and f o r the absolute c a l i b r a t i o n instruments. L i v i n g quarters were b u i l t on Koror but on Guam were made a v a i l a b l e through the cooperation of the National Bureau of Standards, Instrumentation a t both observatories was t h a t of a f i r s t - c l a s s standard magnetic observatory, w i t h f u l l absolute c o n t r o l of base-line values, and w i t h standard-speed and rapid-run magnetographs of normally h i g h s e n s i t i v i t y , 3, Personnel, The p r o j e c t was under the general supervision of E, B, Roberts, J, H. Nelson, and Joel B, Campbell, 4, Data, Data have been processed and published, or are a v a i l a b l e on m i c r o f i l m as discussed under Project 3,1, A l l data from the IGY period have been submitted to the data centers, 5, Results, While t h i s was p r i n c i p a l l y a data c o l l e c t i n g p r o j e c t , some study of the enhancement of daytime a c t i v i t y and the range of d i u r n a l v a r i a t i o n a t Koror has been made by s c i e n t i s t s of the Survey and copies of records have been furnished t o other i n v e s t i g a t o r s f o r a n a l y s i s . Since the IGY, the magnetic observatory a t Guam has been continued by the Coast and Geodetic Survey as a permanent part of regular f i e l d operations, 6, Bibliography. Knapp, David G.: "Some IGY Geomagnetic Results i n the P a c i f i c , and a Suggestion as t o the O r i g i n of the Equatorial E l e c t r o j e t . " (Processed). U. S. Coast and Geodetic Survey, 1958, 9 pp. GettenQT, John W,: "Magnetic Daily V a r i a t i o n a t Koror," Joum, Geophys. Res,, v o l , 67, 1962, pp, 1885-1888, Knapp, David G,, John W, Gettemy: "A New Longitude E f f e c t i n the Geomagnetic Solar Dally V a r i a t i o n , " Journ. Geophys, Res,, v o l , 68, 1963, pp, 2411-2420, 132

GEOMAGNETISM Proj e c t 3,4 - East-West Network of Magnetic Recording Stations 1, Objectives, Inasmuch as there had been some I n t e r e s t during the past decade or so i n possible c o r r e l a t i o n between geomagnetic a c t i v i t y and meteorological changes— possibly through mass movement of atmospheric " c e l l s " and possible d i f f e r e n t i a l i o n i - z a t i o n i n the high atmospheres—it was expected t h a t the east-west chain of magnetic recorders i n s t a l l e d by the U. S, Coast and Geodetic Survey would y i e l d magnetic data u s e f u l i n such studies, 2, Operations, Five magnetic recording s t a t i o n s were i n s t a l l e d on an east-west l i n e approximately 350 kilometers apart a t L e a d v i l l e , Colorado; B u r l i n g t o n , Colorado, P r i c e , Utah; B e l o i t , Kansas; C a r r o l l t o n , Missouri; I n a d d i t i o n , two other s t a t i o n s , Espanola, New Mexico, and Casper, Wyoming, provided a short north-south i n t e r s e c t i n g l i n e . The s t a t i o n s were equipped w i t h Askania Variographs, a semi-portable 3-component magnetic recorder. Because the instruments were a r e l a t i v e l y new type, there was oft e n d i f f i c u l t y i n securing s a t i s f a c t o r y continuous operation, and the p r e c i s i o n of time marking on the magnetograms was sub-standard because of non-uniform f i l m speed. I n s p i t e of these d i f f i c u l t i e s , however, recordings of considerable value were ob- tained. The Instruments were l e f t unattended i n s p e c i a l l y constructed shelters and were serviced p e r i o d i c a l l y t o remove records, replace f i l m , and make adjustments i n c a l i - b r a t i o n s , e t c , 3, Personnel, The p r o j e c t was under the supervision of E, B, Roberts, J, H. Nelson and Joel B, Campbell, 4, Data, Data have been processed, published, or are a v a i l a b l e on m i c r o f i l m as d i s - cussed under Project 3,1, A l l IGY data have been supplied t o the data centers, 5, Results, Records from t h i s p r o j e c t have been furnished t o research s c i e n t i s t s and s i g n i f i c a n t papers were published i n the s c i e n t i f i c l i t e r a t u r e concerning magnetic storms and magnetic e f f e c t s of high a l t i t u d e nuclear explosions i n the P a c i f i c (actu- a l l y not part of the IGY program). 133

GEOMAGNETISM Project 3,5 - North-South Network (Alaska) of Magnetic Recording Stations 1. Objectives, The o r i g i n a l i n t e n t of the north-south array of magnetic recording s t a t i o n s i n s t a l l e d by the U. S. Coast and Geodetic Survey was to supplement the three standard Alaskan magnetic observatories — Barrow, College, and Sitka — i n obtaining a general coverage of v a r i a t i o n s of the geomagnetic f i e l d m and across the a u r o r a l zone. This would permit the p o s t u l a t i o n and study of e l e c t r i c currents i n the iono- sphere t h a t would cause or be associated w i t h the observed vector changes i n the mag- n e t i c f i e l d , leading to b e t t e r understanding of a l l the r e l a t e d phenomena i n c l u d i n g a u r o r a l a c t i v i t y , ionospheric physics, cosmic rays, and space f i e l d s i n general. 2. Operations. Each recording s t a t i o n consisted of a 3-component Askania Variograph i n s t a l l e d i n a prefabricated non-magnetic aluminum instrument s h e l t e r . I n s t a l l a t i o n s were made a t Barter I s l a n d , Kotzebue, Fort Ytikon, Anchorage, Northway. I n general, the performance of the instruments was reasonably good, although the non-uniformity of f i l m speed l e f t soiriething to be desired i n the way of precise time c o n t r o l on the records. 3. Personnel. The p r o j e c t was under the supervision of E. B. Roberts, J. H. Nelson and Joel B. Campbell. 4. Data. Data have been processed, published, or are av a i l a b l e on m i c r o f i l m s , as discussed under Project 3.1. A l l IGY data have been supplied t o the data centers, 5. Results. Considerable study of the r e s u l t i n g records, together w i t h other Alaskan magnetic records, has been made by the Geophysical I n s t i t u t e of Alaska and by scien- t i s t s of the Coast and Geodetic Survey. 134

GEOMAGNETISM Projects 3,6 and 3.7 - Magnetic Gradient Studies i n Alaska 1. Obiectives. Although established as separate p r o j e c t s by the U. S, Coast and Geodetic Survey, f o r a d m i n i s t r a t i v e reasons, these two IGY a c t i v i t i e s should be con- sidered as parts of the same p r o j e c t , both c l o s e l y r e l a t e d t o the Alaskan North-South Network of magnetic recording s t a t i o n s . P r i m a r i l y , the College-Big Delta-Healy i n - s t a l l a t i o n was intended f o r gradient studies of the geomagnetic f i e l d . Two sets of t r i p a r t i t e s t a t i o n s were expected to y i e l d data t h a t would permit the more precise d e s c r i p t i o n of e l e c t r i c currents i n the ionosphere associated w i t h disturbances i n the magnetic f i e l d , 2. Operations. The Healy and Big Delta locations were equipped w i t h f i r s t - c l a s s magnetographs f u l l y equivalent t o those a t the College observatory — normal- and l o w - s e n s i t i v i t y recorders employing standard recording speed, and a rapid-run magneto- graph. Healy i s approximately on the same geomagnetic meridian w i t h College, Big Delta approximately on the same geomagnetic p a r a l l e l of l a t i t u d e ; both a u x i l i a r y sta- t i o n s were about 130 kilometers from College. (During the e a r l y planning phases the southern a u x i l i a r y s t a t i o n was r e f e r r e d t o as McKinley Park. The a c t u a l s i t e chosen was a t Healy.) Prefabricated non-magnetic aluminum b u i l d i n g s were used to house the recording instriments and provide a shelter f o r absolute c a l i b r a t i o n measurements a t Healy and Big Delta. A d i f f e r e n t i a l magnetograph, i n s t a l l e d i n two outpost shelters some 10 kilometers to the magnetic south and west of the main c o n t r o l equipment a t College and connected by cable w i t h the College Observatory, was designed to record differences between changes i n the magnetic vector a t the outpost s i t e s and a t the observatory. 3. Personnel. The p r o j e c t was under the supervision of E. B, Roberts, J. H. Nelson and Joel B. Campbell. 4. Data. Data have been processed, published, or are a v a i l a b l e on m i c r o f i l m as d i s - cussed under Project 3,1. A l l IGY data have been supplied to the data centers. 5. Results. Some unexpected r e s u l t s were obtained r e l a t e d to the inhomogeneity of the earth c o n d u c t i v i t y . The records are under study a t the Geophysical I n s t i t u t e of Alaska, and a paper has been prepared by a Coast and Geodetic Survey s c i e n t i s t out- l i n i n g a method f o r f i n d i n g l i n e currents from the d i f f e r e n t i a l records. 6. Bibliography. Hurwitz, Louis, "Differential-Magnetograph Exploration of Line Currents." (Pro- cessed). U. S, Coast and Geodetic Survey, 1958, 16 pp. 135

GEOMAGNETISM Project 3.8 - Operation of Rapid-Run A u x i l i a r y Magnetographs 1, Objectives. This program of the Coast and Geodetic Survey provided f o r recording f l u c t u a t i o n s i n the earth's magnetic f i e l d too r a p i d t o be resolved by the time scale of the standard magnetographs inasmuch as much research by many vjorkers has shovm t h a t a great deal of important information can be obtained from the higher frequency com- ponents of the magnetic f l u c t u a t i o n s , 2, Operations. Instrumentation was b u i l t by Rnska, based on s p e c i f i c a t i o n s of the Coast and Geodetic Survey. Resulting grams are much easier to read and i n t e r p r e t than previously a v a i l a b l e equipment was capable of producing. I n s t a l l a t i o n s were made a t Tucson, Honolulu, S i t k a , College, Point Barrow, Healy, Big Delta, Guam, Koror, L i t t l e America, Byrd and Wilkes. Fredericksburg had already been equipped w i t h a rapid-run magnetograph, 3, Personnel. The p r o j e c t was under the supervision of E. B. Roberts, J. H. Nelson and Joel B, Campbell. 4, Data. Data are a v a i l a b l e on m i c r o f i l m as discussed under Project 3,1. A l l IGY data have been supplied to the data centers, 5, Results, The rapid-run magnetograms are c o n t r i b u t i n g to numerous studies and i n - v e s t i g a t i o n p r o j e c t s , as evidenced by the requests f o r copies o f the grams from World Data Center A. The rapid-run equipment has been i n continuous operation a t the per- manent observatories since the close of the IGY. Project 3,9 - Single Component V i s i b l e Recording Magnetographs 1. Objectives. This p r o j e c t of the Coast and Geodetic Survey was established mainly to a s s i s t the ionospheric physics program t o provide immediately accessible informa- t i o n on magnetic a c t i v i t y . 2. Operations. This p r o j e c t consisted of designing and purchasing magnetic v a r i o - meters ( f o r responding to changes i n D e c l i n a t i o n or Horizon t a l I n t e n s i t y ) and pen- and-ink recorders f o r i n s t a l l a t i o n a t ionosphere s t a t i o n s . The r e s u l t i n g magnetograms were not expected to be of f i r s t - q u a l i t y p r e c i s i o n and are therefore not preserved i n the archives of the IGY World Data Centers. However, judging by the requests f o r the equipment, and comments on i t s usefulness, i t helped to f i l l a r e a l need a t the f o l - lowing l o c a t i o n s : Hanover, N. H.; Un i v e r s i t y Park, Pa.; Boulder, Colo.; Pullman, Wash.; Stanford, C a l i f , ; Sunspot, N, M.; Thule AFB, Greenland; L i t t l e America, Ant- a r c t i c a ; and Knob Lake, Canada. Some t r o u b l e was experienced a t a few of the i n s t a l l a t i o n s , due e n t i r e l y to mal- f u n c t i o n i n g of the recorder u n i t — a moderate p r i c e d , commercially a v a i l a b l e balanc- ing potentiometer device. Where these recorders could be replaced by the users w i t h a b e t t e r q u a l i t y instrument, performance was qui t e s a t i s f a c t o r y , 3. Personnel. The p r o j e c t was under the supervision of E. B. Roberts, J. H. Nelson and Joel B. Campbell. 4. Data. Inasmuch as these instruments were not c a l i b r a t e d and used only f o r a u x i - l i a r y i n f ormation f o r the purposes of other programs, the records were not processed and are r e t a i n e d by the s c i e n t i s t s a t the operating s t a t i o n s . 136

GEOMAGNETISM Project 3.10 - Sub-Audio-Frequency Geomagnetic Fluctuations 1, Obiectives. The objectives of the program, which was a j o i n t e f f o r t of the Geo- physics Research D i r e c t o r a t e (GRD), A i r Force Cambridge Research Center, and the Den- ver Research I n s t i t u t e (DRI), U n i v e r s i t y of Denver, were to obtain a d e s c r i p t i o n of the geomagnetic f l u c t i i a t i o n s i n the 1 t o 50 cps. frequency band and to determine, as fa r as possible, the sources of the f l u c t u a t i o n s . The small amount of data a v a i l a b l e before the I n t e r n a t i o n a l Geophysical Year in d i c a t e d t h a t both atmospheric and iono- spheric sources could c o n t r i b u t e to the s i g n a l w i t h the l a t t e r becoming more important a t the higher l a t i t u d e s . There was also some evidence t h a t i n the a u r o r a l zone the larg e s t f l u c t u a t i o n s tended to precede, by i n t e r v a l s of several hours, the larg e r mag- n e t i c disturbances as measured by the K in d i c e s . 2. Operations. For the f i e l d measurement s t a t i o n s , special equipment was constructed i n c l u d i n g detector c o i l s using mu-metal cores, lo w - l e v e l a m p l i f i e r s using high-gain input transformers, fm modulators, and switching systems t o provide f o r automatic data sampling. Low-speed (0.3 inch/second) magnetic tape t r a n s p o r t s , c a l i b r a t i o n o s c i l l a - t o r s , and power supplies were procured f o r the f i e l d s t a t i o n . Three mutually perpen- d i c u l a r components of the 1 t o 50 c/s f l u c t u a t i o n s were recorded on 1/4 inch magnetic tape during the f i f t e e n - m i n u t e i n t e r v a l from 02 to 17 minutes a f t e r each hour. For the c e n t r a l monitoring s t a t i o n a t DRI, a standard tape recorder (30 inches/second f o r playback), octave band-width f i l t e r s covering the 1 t o 50 c/s range, and pen-and-ink recorders were procured. F i e l d recording s t a t i o n s were located a t : Thule, Greenland (June 1958 - Dec. 1958) Fort Devens, Mass. (March 1958 - Dec. 1958) Mt. Evans, Colorado (May 1958 - Dec. 1958) College, Alaska (Sept. 1958 - Dec. 1958) Ramey AFB Since much of the equipment had to be developed e s p e c i a l l y f o r t h i s work, there was considerable delay i n g e t t i n g the s t a t i o n s i n t o operation. Accordingly, opera- tion s were continued w e l l beyond the formal IGY period ( i n f a c t , w e l l i n t o 1960) i n order to secure a representative sample of data. An a d d i t i o n a l s t a t i o n a t Hxiancayo, Peru, was also a c t i v a t e d a f t e r the close of the IGY t o extend the geographic coverage. 3, Personnel. The p r o j e c t was organized and c a r r i e d out under the d i r e c t i o n of Elwood Maple, GRD. Dr. A. R. Jordan, who supervised the p a r t i c i p a t i o n of DRI a t the beginning of the program, has since l e f t t h a t i n s t i t u t i o n , and Dr. A l v i n W, Jenkins i s now i n charge there. Other key personnel have been Don F. Smart (GRD) and Charles Sawyer (employed under co n t r a c t w i t h the American Geographical Society) who operated the Thule s t a t i o n , and a t DRI, Charles A. P h i l l i p s , J r . 4. Data. The data are stored a t DRI on magnetic tapes. Since t h i s was a spe c i a l p r o j e c t w i t h no i n t e r n a t i o n a l counterparts, and because reduction of the data w i t h the o r i g i n a l equipment was an extremely slow process, no data have yet been submitted to the data centers. Since the close of the IGY, however, equipment has been devel- oped f o r automatic data redu c t i o n . Much of the 1958 IGY and the IGC-1959 recordings have now been reduced to tables of average s i g n a l l e v e l s . When r e l i a b i l i t y l i m i t s have been determined f o r the reduced data, they w i l l be made a v a i l a b l e f o r the use of other In t e r e s t e d s c i e n t i s t s . When the tapes are played back, the s i g n a l f o r each of the three components (now i n the 100 t o 5000 c/s range) i s fed t o s i x octave band-pass f i l t e r s , and the output 137

GEOMAGNETISM of each f i l t e r i s r e c t i f i e d and averaged by one of two a l t e r n a t i n g sets of RC c i r c u i t s having time constants of 100 seconds (equivalent t o 10^ seconds of recording t i m e ) . At the end of each 15 minute recording i n t e r v a l (9 seconds a t playback), the condenser voltages are read and punched i n t o paper tape, and the condensers are discharged before t h e i r next c y c l e . These values are then tabulated on a Flex o w r i t e r and may also be fed t o a d i g i t a l computer f o r s t a t i s t i c a l a n a l y s i s . The r e s u l t i n g tables thus contain eighteen values ( s i x frequency bands f o r each of the three components) f o r each hour of the day. 5. Results. A l l analysis to date has been based on average values of s i g n a l l e v e l . Most of the f l u c t u a t i o n s throughout the 1 t o 50 c/s range a r i s e from thunderstorm a c t i v i t y as may r e a d i l y be demonstrated by comparing the d i u r n a l and seasonal v a r i a - t i o n s of s i g n a l l e v e l w i t h the corresponding v a r i a t i o n s of the average worldwide thunderstorm d i s t r i b u t i o n and taking account of the d i r e c t i o n a l e f f e c t s of the detec- t o r c o i l s . Signal l e v e l s i n the 9.8 c/s band (6.8 t o 14.0 c/s) v a r i e d l e a s t as the average distance from the source v a r i e d , and a peak i n the frequency spectrum appeared i n t h i s band when the thunderstorm a c t i v i t y was comparatively d i s t a n t . This consistent feature of the data, when combined w i t h the narrow-band analysis of a small amount of data by Balser and Wagner who resolved the i n d i v i d u a l modes, confirms the resonant modes of the earth-ionospheric c a v i t y ( f i r s t described by Schumann) as a stable fea- ture of the propagation i n t h i s frequency range. The second to f o u r t h modes would also c o n t r i b u t e t o the 19 c/s band. I n the highest frequency band used (center f r e - quency 34 c/s, 25 t o 46 c/s band) the i n d i v i d u a l higher order modes become less s i g n i - f i c a n t , and the estimated a t t e n u a t i o n of somewhat less than 1 db per 1000 km i s i n reasonable agreement w i t h the waveguide theory and observational data a t higher f r e - quencies. Below about 8 c/s (the fundamental resonant mode of the c a v i t y ) a t t e n u a t i o n i n - creases w i t h decreasing frequency, but the wavelengths become so long t h a t the induc- t i o n f i e l d of the source i s o f t e n comparable t o or larger than the r a d i a t i o n f i e l d , and estimates o f a t t e n u a t i o n become somewhat ambiguous. The observed increase of average s i g n a l s t r e n g t h w i t h decreasing frequency below 8 c/s f o r times of compara- t i v e l y close thunderstorm a c t i v i t y ( i . e . , average summer daytime c o n d i t i o n s ) does not agree w i t h c u r r e n t ideas of the power spectrum of the l i g h t n i n g discharge. Possible explanations might be the long c o n t i n t i a t i o n of low c u r r e n t d e n s i t i e s i n the discharge channel as suggested by recent photographic observations or cloud-to-cloud or upward discharges from thunderstorm c e l l s whose spectra might d i f f e r from t h a t of the cloud- t o - e a r t h discharge. Fluctuations of ionospheric o r i g i n also appear i n the records but must be separated from the thunderstorm f l u c t u a t i o n s which u s u a l l y predominate, and t h e i r analysis has only begun. At middle l a t i t u d e s t a t i o n s there i s l i t t l e r e l a t i o n s h i p between average s i g n a l l e v e l s and the K indices of geomagnetic a c t i v i t y , but a weak c o r r e l a t i o n may be observed i n the 1 to 4 c/s range when the thunderstorm f l u c t u a t i o n s are q u i t e small ( i . e . , average w i n t e r n i g h t c o n d i t i o n s ) . P r i o r t o the s t a r t of t h i s program, single-component measurements a t Point Barrow, Alaska, had shown increased s i g n a l l e v e l s preceding by several hours many of the l a r - ger magnetic disturbances as measured by the l o c a l K indices. Examination of small amounts o f data from College, Alaska, and Thule, Greenland, has revealed a few events of t h i s type a t College, but none a t Thule. I f f u r t h e r analysis confirms these r e - s u l t s , such events could not be a t t r i b u t e d t o e f f e c t s of solar p a r t i c l e r a d i a t i o n i n the lower ionosphere, but the generation of hydromagnetic waves a t the outer f r i n g e of the geomagnetic f i e l d , as suggested by Parker, might be ap p l i c a b l e . 138

GEOMAGNETISM Enhanced s i g n a l l e v e l s a t t r i b u t e d to meteor e f f e c t s i n the lower ionosphere are sometimes observed, p a r t i c u l a r l y under w i n t e r n i g h t c o n d i t i o n s , i n the 1 t o 2 and 2 to 4 c/s bands. The evidence f o r such e f f e c t s i s strong bat not yet conclusive, and f u r t h e r i n v e s t i g a t i o n s are under way. Many special types of waveforms, probably a t t r i b u t a b l e to ionospheric phenomena, have o f t e n been observed i n the course of f i e l d s t a t i o n operation, and i t i s hoped t h a t equipment w i l l become a v a i l a b l e i n the f u t u r e f o r a systematic survey of the c h a r a c t e r i s t i c s of these phenomena i n the extensive tape recordings which have been accumulated. 6. Bibliography. a. Papers Presented a t Meetings. E. Maple: "Sub-Audio-Frequency Geomagnetic F l u c t u a t i o n s . " F o r t i e t h Annual Meeting, American Geopl^sical Union, Washington, D. C, May 4-7, 1959. E. Maple, A, W. Jenkins, C, A. P h i l l i p s : "Sub-Audio-Freqoency Geomagnetic Fluctuations a t Denver, Colorado," F o r t y - F i r s t Annual Meeting, American Geophysical Union, Washington, D. C, A p r i l 27-30, 1960, A. W. Jenkins, C. A. P h i l l i p s , E. Maple: "Observed C o r r e l a t i o n Between Geomagnetic Fluctuations and Meteor Rates," F o r t y - F i r s t Annual Meeting, American Geophysical Union, Washington, D, C., A p r i l 27-30, 1960, E. Maple: "Sub-Audio-Frequency ( 1 t o 50 cps) Geomagnetic Fluc t u a t i o n s . " I n t e r n a t i o n a l Association of Geomagnetism and Aeronomy, X I I General Assembly of lUGG, H e l s i n k i , Finland, July-August 1960. b. Published Papers: A. W. Jenkins, C. A. P h i l l i p s , and E. Maple: "Observed Magnetic E f f e c t s from Meteors." .JGR, v o l . 65, no. 5, May 1960, pp. 1617-1619. 139

GEOMAGNETISM Project 3.11 - Magnetic Observations a t J a r v i s , Palmyra and Fanning 1. Objectives. Temporary magnetic observatories were established under t h i s p r o j e c t , and operated f o r about one year during the IGY, by the Scripps I n s t i t u t i o n of Oceano- graphy, Uni v e r s i t y of C a l i f o r n i a , La J o l l a , C a l i f o r n i a , on J a r v i s , Palmyra and Fan- ning Islands, and f o r one month on Christmas I s l a n d , f o r the purpose of studying the anomalous behavior of the magnetic f i e l d i n the v i c i n i t y of the magnetic equator. 2. Operations. The bulk of the instrumentation required f o r the p r o j e c t was procured, from other funds, by the Coast and Geodetic Survey. This included three three-compo- nent Askania Variographs, recording changes of D, H and Z, three contact clocks f o r providing time marks on the variograph records, three chronometers, and two theodo- lite-magnetometer-inductors f o r absolute determinations of D, H and I , The Coast Survey also provided f a c i l i t i e s f o r t r a i n i n g the observers. The Scripps I n s t i t u t i o n undertook r e s p o n s i b i l i t y f o r a l l other aspects of the p r o j e c t , f o r engaging personnel, f o r providing shelters and the necessary power supplies f o r the recording equipment, and f o r l o g i s t i c support of the operation, i n c l u d i n g communications. Because of the remoteness of the Line Islands and the i m p o s s i b i l i t y of maintaining day-to-day c o n t r o l of the operation from Scripps i t was decided t o appoint a F i e l d Party Chief who would be f u l l y responsible f o r a l l aspects of the f i e l d operation. Further, because of the inhospitable nature of J a r v i s , i t was decided t h a t a boat should be permanently a v a i l a b l e i n the area f o r supplies, r e l i e f of personnel and emergency use. These two requirements were met by ch a r t e r i n g a s a i l i n g boat, w i t h a u x i l i a r y engine, capable of s a i l i n g between Hawaii and the Line Islands and w i t h a captain who was q u a l i f i e d to act as F i e l d Party Chief. The l a t t e r was assisted by three t r a i n e d observers and by one f u l l - t i m e and several part-time a s s i s t a n t s . I t was i n i t i a l l y planned to make measurements over a period of about 15 months. However, i t turned out t h a t J a r v i s and Fanning operated f o r a l i t t l e over 16 months, w i t h about 807» complete records, and Palmyra f o r 12 months, w i t h 50% complete records. Most of the gaps were due to instrumental t r o u b l e s , some of which required spare parts to be obtained from the mainland. The Jarvis s t a t i o n was closed down f o r three weeks during October 1958 because of the death of the observer. The Palmyra s t a t i o n was tran s f e r r e d to Christmas Island f o r the month of December 1958. Invaluable assistance was obtained from the B r i t i s h a u t h o r i t i e s , who l e f t i n t a c t on Jarvis the i n s t a l l a t i o n s provided f o r a s c i e n t i f i c party working i n the area p r i o r to the beginning of the p r o j e c t and who a i r l i f t e d both personnel and supplies between Hawaii and Christmas I s l a n d , The B r i t i s h company. Cable and Wireless, generously made av a i l a b l e to the p r o j e c t the supply, workshop and s o c i a l f a c i l i t i e s of t h e i r cable s t a t i o n on Fanning I s l a n d . 3. Personnel. The pr o j e c t was under the general supervision of Dr. Ronald Mason of the Scripps I n s t i t u t i o n who v i s i t e d the Line Islands during the setting-up phase and towards the end of the operating period and who provided l i a i s o n between Scripps and the f i e l d p r o j e c t on s c i e n t i f i c matters. Dr. Martin Vitousek was the F i e l d Party Chief and skippered his own vessel, the FIESTA, f o r supply operations. 4. Data. Data from J a r v i s have been processed and published as Coast and Geodetic Survey P u b l i c a t i o n HV-JI58. Data from Fanning w i l l be d e a l t w i t h s i m i l a r l y . A l l other data from the IGY period have been submitted to the data centers and are a v a i l - able on m i c r o f i l m as discussed under p r o j e c t 3.1. 5. Bibliography. R. G, Mason and M. J. Vitousek. "Some Geomagnetic Phenomena Associated w i t h Nuclear Explosions." Nature, v o l . 184, pp. B. A. 52-54, 1959. E x p l o i t a t i o n of the data i s the subject of an NSF grant to the Scripps I n s t i t u - t i o n , Grant Y/22.12/312 - Line Islands Geomagnetic Data. 140

COSMIC RAYS Ph.D. Thesis, U n i v e r s i t y of Missouri, 1962). The underground c o n f i g u r a t i o n i n t h i s experiment i s q u i t e s i m i l a r to that i n the Valmeyer mine. The adjusted depth i n - cludes a standard equivalent v e r t i c a l atmosphere (only to f a c i l i t a t e comparison w i t h other data) and a l o c a l t h i c k s h i e l d which was traversed by a l l the p a r t i c l e s . The f r a c t i o n a l counts r e s u l t from a simple s t a t i s t i c a l treatment of events i n v o l v i n g small e l e c t r o n showers. The r e s u l t s of both experiments confirm a l l the e s s e n t i a l conclusions of the ear- l i e r t h e o r e t i c a l c a l c u l a t i o n s (Smith and D u l l e r , 1959). I n a d d i t i o n to these i n t e g r a l i n t e n s i t i e s of muons, inferences from the data include the f o l l o w i n g (R.R. Kasten, Ph.D. Thesis, U n i v e r s i t y of Missouri, 1962). i n t e g r a l and d i f f e r e n t i a l muon energy spectra, production spectrum of high-energy pions i n the atmosphere, absorption mean- free-path of high-energy pions i n the atmosphere, and average muon energies at moder- ate depths underground as a f u n c t i o n of both depth and d i r e c t i o n . 6. Bibliography. a. Papers Presented at Meetings. J.A. Smith and N.M. D u l l e r : "Theory of Zenith-Angle V a r i a t i o n of the I n t e n - s i t y of High-Energy Mu-Mesons." B u l l e t i n of the American Physical Society, v o l . 3, no. 7, Nov. 1958, p. 362. W.R. Sheldon and N.M. D u l l e r : " I n t e n s i t y of High-Energy Mu-Mesons at Large Zenith Angles." B u l l e t i n of the American Physical Society, v o l . 5, no. 1 (Part I ) , January 1960, p. 23. W.R. Sheldon and N.M. D u l l e r : "High-Energy Cosmic Ray Mu-Mesons at Large Zenith Angles." Midwest Cosmic Ray Conference, St. Louis, Missouri, March 1961. O.L. Smith and N.M. Duller- "Muons at Large Zenith Angles." B u l l e t i n of the American Physical Society, v o l . 7, no. 4, A p r i l 1962, p. 310. N.M. D u l l e r : "Cosmic Ray Muons at High Energies." I n v i t e d Paper before National Academy of Sciences, Austin, Texas, December 1962. R.R. Kasten and N.M. D u l l e r : "High-Energy Pions and Muons i n the Atmosphere." B u l l e t i n of the American Physical Society, v o l . 9, no. 2, Feb. 1964, p. 141. b. Published Papers. J.A. Smith and N.M. D u l l e r : " E f f e c t s of Pi-Meson Decay-Absorption Phenomena on the High-Energy Mu-Meson Ze n i t h a l V a r i a t i o n near Sea Level." JGR, v o l . 64, no. 12, Dec. 1959, pp. 2297-2305. W.R. Sheldon and N.M. D u l l e r : " I n t e n s i t i e s of Muons Underground at Large Zenith Angles." Nuovo Cimento. v o l . 23, Jan. 1962, pp. 63-76. O.L. Smith, R.R. Kasten, and N.M. D u l l e r : "Cosmic Ray Muons at High Energies." ( I n preparation.) 109

COSMIC RAYS Table I I I . Experimental data of an underground experiment at P r a i r i e du Rocher, I l l i n o i s , (near sea l e v e l ) g i v i n g absolute cosmic ray muon i n t e n s i t i e s . Operating s t a t i o n and Zenith angle Rock thickness (rawe) Adjusted depth (mwe) Error: l 2 % T o t a l counts T o t a l f r a c t i o n a l counts I n t e n s i t y of muons ( p a r t i c l e s _ ^ cm" s t " sec X 10"5) 71° 81.6 96.9 215.0 14.0 18.01±1.23 74° 80.3 95.6 548.8 29.8 16.09± .69 77° 79.2 94.3 991.2 47.2 13.45± .43 1 80° 78.4 93.7 1089.5 46.5 11.09± .34 83° 77.8 93.1 879.5 21.5 7.931 .27 86° 77.3 92.6 343.9 12.9 5.16+ .28 89° 77.2 92.5 47.5 1.5 2.21± .32 71° 74° 77° 80° 83° 86° 89° 117.8 115.3 113.8 112.6 111.7 111.1 110.9 133.1 130.6 129.1 127.9 127.0 126.4 126.2 207.2 577.0 1018.8 1098.8 823.4 309.5 39.0 12.2 32.0 40.8 46.8 44.4 18.5 4.0 12.70± 11.081 10.16+ 8.72? 6.49± 4.13± 1.66+ .88 .50 .32 .26 .28 .23 .26 71° 74° 77° 80° 83° 194.4 192.6 160.1 148.4 147.3 209.7 207.9 175.3 163.7 162.6 274.1 826.9 1364.3 816.9 217.7 17.1 40.9 64.3 49.9 16.7 13l .43 ,74+ 23 20 66± .23 53+ 6 6 l ,38 71° 250.6 265.9 266.8 10.8 5.23± .29 74° 239.5 254.8 794.8 37.8 4.88± .17 4 77° 226.5 241.8 1146.3 42.3 4.761 .16 80° 208.6 223.9 774.2 31.2 4.751 .17 83° 176.1 191.4 231.1 12.1 4.53+ .30 77° 356.7 372.0 672.1 31.1 2 . 5 l l .10 5 80° 334.2 349.5 422.7 20.7 2.331 .11 4. 83° 298.7 314.0 122.5 6.5 2.161 .19 6 68° 23.1 38.4 1149.9 33.9 56.3±1.7 110

COSMIC RAYS Project 2.25 - Solar E f f e c t s on Cosmic Rays at High A l t i t u d e s - A r c t i c 1, Objectives. This p r o j e c t at the State U n i v e r s i t y of Iowa, provided f o r high a l - t i t u d e balloon measurements of cosmic-ray i n t e n s i t y , c a r r i e d out at a high l a t i t u d e during the IGY. Emphasis was placed on regular long-duration balloon f l i g h t s , par- t i c u l a r l y during solar disturbances and aur o r a l a c t i v i t y i n order to obtain any cor- r e l a t i o n s of these events w i t h cosmic ray phenomena. a. Following types of measurements were planned: ( i ) The rate of a single Geiger counter, to measure the average omnidirec- t i o n a l charged p a r t i c l e i n t e n s i t y above a very low c u t o f f energy. ( i i ) The r a t e of a v e r t i c a l counter telescope, to measure the v e r t i c a l d i r e c - t i o n a l charged p a r t i c l e f l u x . ( l i i ) The t o t a l current of a Neher type i o n i z a t i o n chamber. ( i v ) The r a t e of a t h a l l i u m a c t i v a t e d Nal c r y s t a l ( f o r the 1958 f l i g h t s ) as an X-ray detector, w i t h c i r c u i t r y to count pulses w i t h lower l i m i t s of 40, 80, 160, 400 kev. b. The o r i g i n a l o bjectives of these f l i g h t s were: ( i ) To study the properties of the low energy end of the cosmic-ray energy spectrum, p a r t i c u l a r l y i t s time v a r i a t i o n over the period of one month (or one solar r o t a t i o n ) . More s p e c i f i c a l l y i t was desired to examine the time v a r i a t i o n of the en- ergy region to which ground l e v e l neutron monitors are i n s e n s i t i v e . ( i i ) To study Impact zone and small f l a r e e f f e c t s at n o r t h e r l y l a t i t u d e s . ( i i i ) To search f o r s o f t r a d i a t i o n at moderate atmospheric depths of 10 gm/cm . 2. Operations. Through the cooperation o f D.C. Rose and the Canadian IGY Committee arrangements were made f o r a series of high a l t i t u d e balloon f l i g h t s from Fort Church- i l l , Canada. I t was hoped to achieve a more-or-less continuous monitor at high a l t i - tude of the cosmic ray f l u x and r e l a t e d phenomena. At the same time, monitor f l i g h t s were c a r r i e d out by the group at the U n i v e r s i t y of Minnesota at Minneapolis, at ap- proximately the same longitude but about 13° to the south. During the period of 7 August to 7 September 1957, fourteen high a l t i t u d e balloons bearing cosmic-ray instrumentation were launched from Fort C h u r c h i l l , Canada, l a t i t u d e 58.8°N., longitude 94.2° W. The t o t a l d u r a t i o n of these f l i g h t s which occurred w i t h - i n telemetering range was about 250 hours w i t h 175 hours occurring above 30 km a l t i - tude. F l i g h t s g i v i n g up to 25 hours of usable data were a t t a i n a b l e because of the low wind speeds at a l l a l t i t u d e s reached above 27 km. Between 10 August and 17 September 1958, twelve high a l t i t u d e , constant l e v e l balloons c a r r y i n g cosmic-ray instrumentation were launched from Fort C h u r c h i l l , Man- it o b a , Canada (Lat. 58.8''N, Long. 94.2°W). The purpose of these f l i g h t s was to ob- t a i n i n f o r m a t i o n on high l a t i t u d e cosmic ray e f f e c t s and X rays occurring i n connec- t i o n w i t h magnetic storms and other geophysical or solar phenomena. Approximately 150 hours of data were obtained above 30 km a l t i t u d e . To continue t h i s program of auroral zone measurements, f i v e f l i g h t s were made from Fairbanks, Alaska, during A p r i l 1959 under d i r e c t sponsorship of the ONR Skyhook program. The f l i g h t s were part of the U.S. program during IGC-59. This s i t e was chosen because of the very low 111

COSMIC RAYS ground winds encountered there which would f a c i l i t a t e launching large volume balloons. Such high a l t i t u d e f l i g h t s gave the p o s s i b i l i t y of studying X ray e f f e c t s at very small atmospheric depths. During July 1959 8 f l i g h t s were made from Resolute Bay, 160 km from the North Magnetic Pole, under NSF sponsorship and r e s u l t s on solar pro- tons obtained. Several f l i g h t s were also c a r r i e d out from Fort C h u r c h i l l i n August under ONR sponsorship. 3. Personnel. This work was supervised and c a r r i e d out by Kinsey A. Anderson (now at U. C a l i f . , Berkeley), D.C. Enemark and many other students were also associated w i t h the p r o j e c t and provided invaluable help. 4. Data. Reduced data from the C h u r c h i l l f l i g h t s were published and submitted to the IGY World Data Centers. 5. Results. The d i u r n a l v a r i a t i o n of the cosmic r a d i a t i o n was determined w i t h q u i t e high p r e c i s i o n w i t h the omnidirectional detector. As an example, during the f l i g h t o f August 14, 195 7, the i o n chamber showed an increase o f 3.6 percent between 0800 and 1230 l o c a l time. During the cosmic-ray decrease of 29 August 1957, the change at a l t i t u d e as ob- served by the i o n i z a t i o n chamber was only a f a c t o r of two larger than e x h i b i t e d by the ground l e v e l neutron monitor at C h u r c h i l l . This rather small f a c t o r was a t t r i b u t e d t o the high average energy of the cosmic r a d i a t i o n at sunspot maximum, and confirmed the high e f f i c i e n c y of the neutron monitor at such energies. These f l i g h t s also gave confirming evidence of the a n t i - c o r r e l a t i o n , discovered by Neher and Forbush, between cosmic-ray i n t e n s i t y and solar a c t i v i t y . Just previous to these f l i g h t s , the Minneapolis group (see p r o j e c t 2.12) discovered t h a t s o f t r a d i - a t i o n (X rays) penetrated deeply i n t o the atmosphere. The C h u r c h i l l f l i g h t s uncovered two cases where s o f t r a d i a t i o n appeared; one case (August 29-30, 1957) was p a r t i c u - l a r l y s i g n i f i c a n t because i t occurred during the sudden commencement of a magnetic storm. This r e s u l t opened the p o s s i b i l i t y of c o r r e l a t i v e studies w i t h other geophys- i c a l phenomena. The event of September 1-2, 1957, was not associated w i t h a magnetic disturbance, although i t occurred i n a period of considerable solar a c t i v i t y . The r a d i a t i o n was apparently present before the balloon reached c e i l i n g a l t i t u d e and was s t i l l detectable twelve hours l a t e r . The i o n chamber to single counter r a t i o under- went changes by a f a c t o r of three during the f l i g h t s , p a r t i c u l a r l y i n the e a r l y p a r t . During the greater part of the event, t h i s r a t i o was c h a r a c t e r i s t i c of 100 kev X rays but at times solar protons of average energy 50 to 100 mev at the detectors were prob- ably present. On August 22, 1958, the occurrence of i o n i z i n g r a d i a t i o n was observed i n time as- s o c i a t i o n w i t h a great continuum radio noise storm on the sun. The rates of the i o n chamber and counter telescope rose by as much as a f a c t o r of ten above the cosmic-ray l e v e l while the single counter increased by a much smaller f a c t o r . These r a t i o s could not be obtained w i t h X rays, high energy gamma-rays or electrons, but could be explain- ed by protons of 170 mev energy. The a r r i v a l of these protons, f o l l o w i n g a solar se- quence of o p t i c a l f l a r e , radio noise bursts, and long enduring noise storm, continued to be observed f o r at least two days. From the resemblance of the continuum radio noise emission to the observed p a r t i c l e i n t e n s i t i e s i t was deduced that the cosmic ray storage took place i n the solar atmosphere. The i n t e r p r e t a t i o n of the Fort C h u r c h i l l r e s u l t s was published i n 1958 and estab- lished f o r the f i r s t time solar production of nucleonic p a r t i c l e s i n the energy region 100 t o 300 Mev. Shortly a f t e r the preliminary r e s u l t s were published the r e l a t i o n o f these solar p a r t i c l e fluxes to the absorption of g a l a c t i c radio noise i n riometers located i n the polar regions was noticed. This led to a very r a p i d development of the study of low energy solar cosmic rays. 112

COSMIC RAYS Simultaneous balloon f l i g h t s by the Minnesota cosmic ray group at Minneapolis g r e a t l y extended the conclusions that could be drawn from t h i s experiment. The pres- ence of Explorer IV i n i t s o r b i t also added very s u b s t a n t i a l l y to the experiment and represented the f i r s t time t h a t the simultaneous use of the balloon and s a t e l l i t e techniques yielded important s c i e n t i f i c r e s u l t s . 6. Bibliography. a. Papers Presented at Meetings. The r e s u l t s of the pr o j e c t were described at various meetings, i n c l u d i n g , American Physical Society meeting m St. Louis, Nov. 1957, Washington, D.C., 1958, 1959 and 1960; the Mid West Cosmic Ray Meeting, Iowa C i t y , October 1959; and the COSPAR Space Science Symposium, Nice, France, February 1960. b. Published Papers. K.A. Anderson: "Occurrence of Soft Radiation During the Magnetic Storm of 29 August 1957." JGR, v o l . 62, 1957, pp. 641-44. K.A. Anderson: "Soft Radiation Events at High A l t i t u d e during the Magnetic Storm of August 29-30, 1957." Phys. Rev., v o l 111, no. 5, Sept. 1, 1958, pp. 1397-1405. K.A. Anderson: " I o n i z i n g Radiation Associated w i t h Solar Radio Noise Storm." Phys. Rev. L e t t e r s , v o l . 1, no. 9, Nov. 1, 1958. K.A. Anderson, R. Arnoldy, R. Hoffman, L. Peterson, J.R. Winckler: "Observa- ti o n s of Low Energy Solar Cosmic Rays from the Flare of 22 August 1958." JGR. v o l . 64, no. 9, Sept. 1959, pp. 1133-48. K.A. Anderson, D.C. Enemark: "Balloon Observations of X-Rays i n the Auroral Zone I . " JGR, v o l . 65, no. 2, Feb. 1960, pp. 551-64. K.A. Anderson, D.C. Enemark: "Balloon Observations of X-Rays i n the Auroral Zone I I . " JGR, v o l . 64, no. 11, Nov. 1960, pp. 3521-38. D.C. Enemark, K.A. Anderson: "Instrumentation f o r Auroral Zone Balloon Ex- periments and Summary of F i e l d Operations." Phys. Dept., State Univ. of Iowa, Report SUI-59-17, June 1959. K.A. Anderson "Solar P a r t i c l e s and Cosmic Rays." S c i e n t i f i c American, v o l . 202, no. 6, 1960, pp. 64-71. K.A. Anderson and D.C. Enemark: "Observations of Auroral Zone X-Rays and Solar Cosmic Rays." Proc. of the F i r s t I n t e r n a t i o n a l Space Science Symposium. Amsterdam 1960, p. 702. K.A. Anderson and D.C. Enemark: "Observations of Solar Cosmic Rays Near the North Magnetic Pole." JGR, v o l . 65, 1960, p. 2657. 113

COSMIC RAYS Project 2.28 - Neutron Monitor - Thule 1. Objectives. This p r o j e c t , undertaken by B a r t o l Research Foundation of the F r a n k l i n I n s t i t u t e , provided f o r the c o n s t r u c t i o n and i n s t a l l a t i o n of a neutron monitor, as part of an i n t e r n a t i o n a l network of ground l e v e l cosmic ray monitors f o r the IGY. The p i l e was i d e n t i c a l i n design to that at Resolute, Canada, so t h a t a d e t a i l e d study, i n cooperation w i t h Canadian s c i e n t i s t s , of time v a r i a t i o n s and d i s t i n c t i v e events was possible at locations near the geomagnetic pole but at widely d i f f e r e n t longitudes. 2. Operations. The equipment was i n s t a l l e d on the Thule A i r Base, at a f i e l d s i t e operated by the U.S. Army Signal Corps Radio Propagation Agency, personnel of which operated the equipment. 3. Personnel. This work was under the supervision of M.A. Pomerantz. V.R. Potnis was the p r i n c i p a l s c i e n t i s t Involved i n the reduction of data. 4. Data. Data were reduced according to the CSAGI plan and submitted to the IGY World Data Centers. 5. Results. A general o v e r a l l decrease of about 7.57, i n cosmic-ray i n t e n s i t y was ob- served i n the period August 1957 - August 1958. Numerous Forbush-type decreases were also observed. The m a j o r i t y of these were accompanied by magnetic storms, most of which were of the sudden commencement type. The cosmic-ray events were characterized by a very r a p i d f a l l , followed by a gradual recovery. The events i n October 1957 and January and March 1958 were not accompanied by any type of magnetic disturbance. A number of f l a r e s of importance 3+ occurred but no r e l a t e d cosmic-ray increases were observed. Excellent c o r r e l a t i o n was found between measurements at Resolute and Thule, a l - though there were s t r i k i n g cases where the respective changes were opposite i n phase. During August 1957, the c o r r e l a t i o n c o e f f i c i e n t between Thule and Ottawa was +0.98. A s i g n i f i c a n t d i u r n a l v a r i a t i o n outside of atmospheric disturbances has been observed at Thule. The d i u r n a l amplitude i s s l i g h t l y smaller than that observed at Resolute. I t I S d i f f i c u l t to understand a d i u r n a l v a r i a t i o n near the pole. T h e o r e t i c a l calcu- l a t i o n s have been made w i t h the UNIVAC computer, and i t i s found that the f a c t that the magnetic axis does not coincide w i t h the axis of r o t a t i o n of the earth may be r e - sponsible f o r observed d i u r n a l v a r i a t i o n a t Thule. The mean y e a r l y amplitude (Aug. 57 - July 58) at Thule i s .09% and the time of maximum i s at 1312 hours l o c a l time. This experimental r e s u l t i s being studied along w i t h the r e s u l t s of other IGY s t a t i o n s to f i n d the energy spectrum of the d a i l y v a r i a t i o n . This study w i l l also i n d i c a t e i f there i s any lower l i m i t of energy below which there i s no d i u r n a l v a r i a t i o n of cosmic rays. 6. Bibliography. K. Nagashima, V.R. Potnis, M.A. Pomerantz: "Theoretical C a l c u l a t i o n of the Solar D i u r n a l V a r i a t i o n of the Cosmic-Ray I n t e n s i t y . " Nuovo Cimento. 1961 ( i n press). S.P. Duggal, K. Nagashima, M.A. Pomerantz: " R i g i d i t y Dependence of Solar Diur- nal V a r i a t i o n of Cosmic Ray I n t e n s i t y , " J. Geophys. Research ( i n press). M.A. Pomerantz, S.P. Duggal, and K. Nagashima: "Solar D i u r n a l V a r i a t i o n of Cos- mic Ray I n t e n s i t y . " Journal of the Physical Society of Japan, v o l . 17, Suppl. A - I I , pp. 464-468, I n t e r n a t i o n a l Conference on Cosmic Rays and the Earth Storm, (1962). S.P. Duggal and M.A, Pomerantz: "Diurnal V a r i a t i o n of Cosmic Rays Near the Geomagnetic Poles." Proceedings of the I n t e r n a t i o n a l Conference on Cosmic Rays, Jaipur, I n d i a , December 2-14, 1963, 114

COSMIC RAYS Project 2.29 - Energy and Charge Spectrum of Primary Cosmic Radiation 1. Objectives. This p r o j e c t at the U n i v e r s i t y of Rochester provided f o r the exposure of large stacks of stripped emulsion at high geomagnetic l a t i t u d e s , where the a p r i o r i r i g i d i t y i s expected to be low. and at high a l t i t u d e s corresponding to a r e s i d u a l over- head mass of less than 8 gm/cm^, f o r periods of eight to sixteen hours. I t was planned to i n v e s t i g a t e the proton energy spectrum at energies equal to or less than 700 Mev; to search f o r primary D, H^ and He3; to determine the low energy end of the heavy par- t i c l e spectrum (Z equal to or greater than 2 ) ; to study i n t e r a c t i o n s of n u c l e i of Z equal to or greater than 2; to study very high energy i n t e r a c t i o n s . 2. Operations. The emulsion stacks were planned to be flown i n such a manner that they would be positioned i n the proper geometry only a f t e r the balloon had reached f l i g h t a l t i t u d e . To t h i s end a mechanism (stack f l i p p e r ) was constructed at Rochester and i n s t a l l e d i n a large p l a s t i c gondola purchased from L.C. Renslow of St. Paul, Min- nesota. Associated timing and pressure recording apparatus was purchased from Raven I n d u s t r i e s , Sioux C i t y , South Dakota. The e n t i r e assemblies when prepared f o r f l i g h t weighed approximately 70 Kg. Two separate balloon f l i g h t s were obtained. The f i r s t f l i g h t ( I ) package consisted of 150 - 25cm x 30cm x 400 micron and 125 - 25cm x 30cm x 600 micron I l f o r d G-5 s t r i p - ped emulsions packed as a single u n i t . The 150 - 400 micron emulsions are the con- t r i b u t i o n s of t h i s laboratory, 90 of the 600 micron emulsions are the c o n t r i b u t i o n s of Dr. M. Friedlander of Washington U n i v e r s i t y , St. Louis, Mo. (performing research under AF Contract No. AF 18(603)-108 and 35 of the 600 micron emulsions were exposed f o r Dr. Charles Dahanayake of the U n i v e r s i t y of Ceylon, Colombo, Ceylon. I t was f e l t t h at the assembly of t h i s large amount of emulsion i n t o one stack enhanced the value of the whole. The exposure was w i t h the 25cm edge h o r i z o n t a l . The second f l i g h t ( I I ) package consisted of 150 - 25cm x 20cm x 600 micron I l f o r d G-5 stripped emulsions and was exposed w i t h the 20 cm edge h o r i z o n t a l . F l i g h t I was launched from Minneapolis, Minnesota (geomagnetic l a t i t u d e 55° N), on Ju l y 30, 1957. The plane of the emulsions was held h o r i z o n t a l u n t i l a f t e r the b a l - loon had reached c e i l i n g at which time i t was rot a t e d 90°. The e f f e c t i v e c o l l e c t i o n time at a l t i t u d e f o r cosmic ray events was 8 hr. 31 min. w i t h the average amount of re s i d u a l atmosphere above the balloon being 8.5 gm/cm^; to account f o r the packing m a t e r i a l and the 1/4" f i b r e glass gondola, the e f f e c t i v e amount of overhead m a t e r i a l was 8.8 gm/cm^. Launch time was 06:30 l o c a l , a l t i t u d e a t t a i n e d at 08:27 and gondola released at 17:55. F l i g h t I I was launched from Neepawa, Manitoba, Canada (geomagnetic l a t i t u d e 61° N) on 3 August 1958. The f l o a t i n g a l t i t u d e corresponded t o 3.5 gm/cm2 of r e s i d u a l a t - mosphere and w i t h the packing and gondola m a t e r i a l , the e f f e c t i v e amount of overhead ma t e r i a l was 3.8 gm/cm^. The e f f e c t i v e exposure time at a l t i t u d e was 8 hours and 30 minutes. Launch was at 05:10 ( l o c a l ) , a l t i t u d e a t t a i n e d at 08:00 and cut down at 16:30. Both operations were arranged v i a the ONR Skyhook Program administered by Commander Cochran of the U n i v e r s i t y of Minnesota. 3. Personnel. This p r o j e c t was under the supervision of M.F. Kaplon. P a r t i c i p a t i n g personnel at the U n i v e r s i t y of Rochester included M.V.K. Appa Rao, A. Engler, A. Kernan, J. Klarmann, and P.J. Lavakare. These p h y s i c i s t s p a r t i c i p a t e d i n various as- pects of data reduction and analysis. 4. Data. Data i s contained i n work submitted f o r p u b l i c a t i o n (see Biblio g r a p h y ) . 115

COSMIC RAYS 5. Results. The i s o t o p i c composition of low energy helium n u c l e i was determined i n the emulsion stacks of both F l i g h t s I and I I by using the "constant s a g i t t a " s c a t t e r - ing method on tracks of helium n u c l e i stopping i n the nuclear emulsion. For F l i g h t I the c r i t e r i a applied was to accept tracks w i t h z e n i t h angles less than 30°, p o t e n t i a l range of 30 cm. and a minimum range of 4.5 cm. For F l i g h t I I the c r i t e r i a were z e n i t h angles less than 45° and minimum range of 4 cm. I d e n t i c a l experimental procedures i n measurement were applied i n both cases. For both f l i g h t s , there was no i n d i c a t i o n of unusual solar a c t i v i t y . For F l i g h t I the r a t i o R = He-^/(He^ + He^) was found to be 0.41 ± 0.09 f o r the en- ergy per nucleon range of 200 to 400 Mev and 0.36 ± 0.11 f o r the magnetic r i g i d i t y range, 1.3 to 1.6 Bv. The c o r r e c t i o n f o r production of secondary He-' i n the r e s i d u a l atmosphere was estimated to be 4%. On the assumption of the non-existence of He i n the primary cosmic ray sources and tha t the observed He-' r e s u l t s from s p a l l a t i o n of higher mass n u c l e i during t h e i r g a l a c t i c t r a v e l , the above fi g u r e s correspond to a t r a v e r s a l of 14 - 3gm/cm" and 12.2 i 3.5 gm/cm^ resp e c t i v e l y of i n t e r s t e l l a r m a t e r i a l . For F l i g h t I I the r a t i o R was determined to be 0.31 ± 0.08 f o r the energy per nu- cleon range of 160-355 Mev, and 0.33 - 0.08 f o r the magnetic r i g i d i t y range 1.05-1.48 Bv. These values are consistent w i t h those observed on F l i g h t I and imply t h a t the observed He^ does not represent a phenomena of l o c a l production w i t h i n the solar system. I n F l i g h t I the He energy spectrum was invest i g a t e d as w e l l as the absolute f l u x . The d i f f e r e n t i a l energy spectrum was observed to have a broad maximum between 400 and 600 Mev/nucleon and appeared to be d i f f e r e n t m shape from the spectra observed at solar minimum. The t o t a l f l u x was observed to be 151 ± 9 He nuclei/m^ sec. s t e r . above the c u t - o f f value f o r the f l i g h t l a t i t u d e . No p a r t i c l e s were observed to have k i n e t i c energies below 200 Mev/nucleon. From the centered dip o l e approximation one would expect a c u t - o f f at 292 Mev/nucleon; the r e s u l t s disagree w i t h t h i s but do not allow a choice to be made between other models. On F l i g h t I I measurements were made to determine the existence of primary deuter- ons and t r i t o n s . The g r a m density vs. range method was used f o r the i d e n t i f i c a t i o n . The s e l e c t i o n c r i t e r i a allowed the observation of deuterons of k i n e t i c energy between 92 and 175 Mev/nucleon and t r i t o n s between 73 and 165 Mev/nucleon. The upper l i m i t s f o r the d i f f e r e n t i a l f l u x e s , i n the ranges defined, were 3.5 x 10"^ and 9.2 x 10"^ particles / m sec. s t e r . Mev f o r deuterons and t r i t o n s r e s p e c t i v e l y . The upper l i m i t f o r the t r i t o n to He r a t i o f o r the same r i g i d i t y (1.14 to 1.48 Bv) i s 0.09. Due to the u n c e r t a i n t y i n the c o r r e c t i o n f o r secondary production w i t h i n the atmosphere, the r e s u l t s are consistent w i t h the absence of these elements w i t h i n the primary cosmic r a d i a t i o n . An a d d i t i o n a l comment about the He r e s u l t s may be made at t h i s p o i n t . Further ex- periments w i t h respect to determining the r a t i o R at low energies have been c a r r i e d out both at Rochester and at other l a b o r a t o r i e s . I n a d d i t i o n the r a t i o of the l i g h t elements ( L ) 3< 5 to the medium n u c l e i (M), 6 < Z< 9 have been c a r r i e d out as a f u n c t i o n of energy, again both at Rochester and at other l a b o r a t o r i e s . These i n d i - cate t h a t the r a t i o L/M increases w i t h decreasing energy and support the observation of a f i n i t e amount of He^ i n the primary r a d i a t i o n . I n conjunction w i t h a lowered r a t i o of L/M at higher energies these r e s u l t s imply that the cosmic r a d i a t i o n at lower energies has traversed more matter than t h a t at higher energies. Whether t h i s r e - f l e c t s p r o p e r t i e s of the source region or of the i n t e r s t e l l a r region i s not yet cl e a r and a d d i t i o n a l measurements as w e l l as t h e o r e t i c a l c a l c u l a t i o n s need yet to be done. 116

COSMIC RAYS 6. Bibliography. a. Papers Presented at Meetings. M.V.K. Appa Rao and M.F. Kaplon: "He^-Nuclei i n the Primary Cosmic Radiation." Journal of the Physical Society of Japan, v o l . 17, Supplement A - I I I , 1962, I n t e r n a t i o n a l Conference on Cosmic Rays and the Earth Storm, Part I I I , pp. 48-52, January 1962. M.F. Kaplon: " I s o t o p i c Composition." Journal of the Physical Society of Japan, v o l . 17, Supplement A - I I I , I n t e r n a t i o n a l Conference on Cosmic Rays and the Earth Storm, Part I I I , pp. 68-73, January 1962. M.V.K. Appa Rao: " I s o t o p i c Composition of Low Energy He Nuclei i n Primary Cosmic Radiation." Am. Phys. Soc, New York January 1961. b. Published Papers. M.V.K. Appa Rao and M.F. Kaplon: "The Influence of I s o t o p i c Composition on the Maximum i n the Cosmic Ray Energy Spectra." I I Nuovo Cimento. Series X, v o l . 21, pp. 369-372, 16 July, 1961. A. Engler, M.F. Kaplon, A. Kernan, J. Klarmann, C.E. F i c h t e l and M.W. Fr i e d - lander: "Primary Cosmic Ray a - P a r t i c l e s - I . " I I Nuovo Cimento. Series X, v o l . 19, pp. 1090-1099, 16 March 1961. M.V.K. Appa Rao: "The He^/ (He^ + He^) Ratio i n Primary Cosmic Radiation." Journal of Geophysical Research, v o l . 67, no. 4, pp. 1289-1293, A p r i l 1962. M.V.K. Appa Rao and P.J. Lavakare: "The Abundance of T r i t o n s and Deuterons i n Primary Cosmic Radiation." I I Nuovo Cimento. Series X, v o l . 26, pp. 740-747, 16 November 1962. M.V.K. Appa Rao: " I s o t o p i c Composition of the Low-Energy Helium Nuclei i n the Primary Cosmic Radiation." The Physical Review, v o l . 123, no. 1, pp. 295-300, 1 July 1961. 117

COSMIC RAYS Project 2.30 - Neutron I n t e n s i t y Time V a r i a t i o n 1. Objectives. This p r o j e c t at the Department of Physics, U n i v e r s i t y of New Hamp- sh i r e , provided f o r reduction o f data from neutron monitor i n s t a l l a t i o n s a t Durham, N.H., and Mt. Washington, the operations of which were supported by non-IGY funds. The f o l l o w i n g i n t e n s i t y - t i m e v a r i a t i o n s were studied: a. 27-day p e r i o d i c i t y b. d i u r n a l v a r i a t i o n c. increases associated w i t h solar f l a r e s d. decreases observed w i t h geomagnetic f i e l d disturbances. 2. Operations. Data from the monitors were reduced t o punch card form and a program w r i t t e n f o r analysis of the data by an IBM 704 or 1620 computer. 3. Personnel. This p r o j e c t was supervised by J.A. Lockwood; J.H. Trainor and Mashea were associated w i t h the work. 4. Data. A l l data from Mt. Washington have been submitted to the IGY World Data Centers. 5. Results. From an analysis of data from Mt. Washington, Mt. Norikura, Japan ( f u r - nished thraugh the cooperation of Y. Miyataki) and Huancayo, from 1954 to 1958, the f o l l o w i n g I n t e r p r e t a t i o n has been made of the long-term v a r i a t i o n . The decline over the period from 1954 to 1958, as w e l l as i n the previous solar cycle, was not a slow gradual process, but occurred i n several sudden drops ( p a r t i c u l a r l y Forbush events) from which only p a r t i a l recovery took place. The Forbush events are probably pro- duced by the passage of the earth i n t o a solar gas cloud; and the continued suppres- sion of the g a l a c t i c i n t e n s i t y and charge i n energy spectrum and c u t o f f r i g i d i t i e s a f t e r some of these events would appear to r e s u l t from the e f f e c t s of these same so- l a r clouds or beams. The analysis of the cosmic ray data from the IGY network during the sudden de- crease of February 11, 1958, was completed. I n that event, the unusual r a p i d i t y of the decrease, which was followed by a temporary recovery at s t a t i o n s o f magnetic l a - t i t u d e less than 50°, provided a c r i t i c a l t e s t f o r e x i s t i n g s o l a r - c o n t r o l l e d modulat- ing mechanisms. The main decrease, which occurred p r a c t i c a l l y simultaneously over the e a r t h , was r e l a t i v e l y energy i n s e n s i t i v e . The subsequent temporary recovery ap- peared to be associated w i t h a s p a t i a l anisotropy. I t i s suggested that these v a r i - a tions can be i n t e r p r e t e d as the r e s u l t of disordering of the outer geomagnetic f i e l d by the solar wind as f i r s t pointed out by E.N. Parker. Further analyses of Forbush events led to the conclusion that the r i g i d i t y depen- dence o f the long term v a r i a t i o n does not agree w i t h t h a t c a l c u l a t e d by Parker f o r the e f f e c t of a h e l i o c e n t r i c s h e l l of disordered magnetic f i e l d s i n the presence of the solar wind; the r i g i d i t y dependence determined by t h i s analysis turned out to be intermediate between the two cases o f d i s o r d e r i n g considered by Parker. And the sa- t e l l i t e observations of Forbush decreases occurring m i l l i o n s of miles i n t o space ex- clude any such geocentric modulation mechanism. Hence, one must consider the e f f e c t upon cosmic rays of an ionized solar gas cloud or beam w i t h dimensions comparable to the earth-sun distance as a minimum. Of the two models thus f a r proposed, the analysis undertaken here favors the " d i f f u s i v e d e c e l e r a t i o n " mechanism proposed by S.F. Singer. The cosmic ray increase o f May 4, 1960, which occurred sixteen minutes a f t e r a class 2 solar f l a r e occurred on the west limb, was studied i n conjunction w i t h solar 118

COSMIC RAYS radio noise data and riometer data. I t was found t h a t the d i f f e r e n t i a l r i g i d i t y spec- trum f o r the p a r t i c l e s produced i n t h i s event was not as steep as found f o r the Febru- ary 23, 1956 event. The d i u r n a l v a r i a t i o n analysis i s not completed as y e t . 6. Bibliography. a. Papers Presented at Meetings. J.A. Lockwood: "On the Long-Term V a r i a t i o n i n the Cosmic Radiation" and "Decrease of Cosmic-Ray I n t e n s i t y on February 1, 1958." F o r t y - F i r s t Annual Meeting, American Geophysical Union, A p r i l 1960, Washington, D.C. b. Published Papers. J.A. Lockwood: "Variations i n the Cosmic-Ray Nucleonlc I n t e n s i t y . " Phys. Rev., v o l . 112, no. 5, 1958, pp. 1750-58. L.L. Towle, J,A. Lockwood: "Cosmic-Ray Increases Associated w i t h Solar Flares." Phys. Rev., v o l . 113, no. 2, Jan. 15, 1959, pp. 641-647. J.A. Lockwood: "On the Long-Term V a r i a t i o n i n the Cosmic Radiation." JGR. v o l . 65, no. 1, Jan. 1960, pp. 19-25. J.A. Lockwood: "Decrease of Cosmic-Ray I n t e n s i t y on February 11, 1958." JGR. v o l . 65, no. 1, Jan. 1960, pp. 27-37. J.E. Henkel, J.A. Lockwood, J.H. Trainor: "A Coiiq>arison of the Cosmic-Ray I n t e n s i t y at High A l t i t u d e s w i t h the Nucleonic Component at Ground Elevation." JGR. v o l . 64, no. 10, October 1959, pp. 1927-38. J.A. Lockwood: "Variations i n the Cosmic Ray Neutron I n t e n s i t y . " U n i v e r s i t y of New Hampshire, Physics Dept., F i n a l Report Contract AF 19(604)-1550. I J.A. Lockwood: "An I n v e s t i g a t i o n of the Forbush Decreases i n the Cosmic Radiation." JGR, v o l . 65, no. 12, Dec. 1960, pp. 3859-80. J.A. Lockwood: "Increase of the Nucleonic I n t e n s i t y on May 4, 1960." (Accepted f o r p u b l i c a t i o n ) , JGR. v o l . 65, no. 10, 1960. J.A. Lockwood: "Intensity-Time V a r i a t i o n of the Cosmic Radiation." A.J. Phys.. v o l . 30, no. 1, January 1962, pp. 10-15. 119

COSMIC RAYS Project 2.32 - Reduction and Analysis of Cosmic-Ray Data 1. Obiectives. This p r o j e c t at the Department of Physics, U n i v e r s i t y of Maryland was set up to provide f o r reduction of data from U. of M. cosmic-ray IGY s t a t i o n s (Wilkes, Thule, Climax, Banff) and f o r analysis of these data i n association w i t h r e - la t e d geophysical phenomena. 2. Personnel. This work was supervised by S.F. Singer, K. Maeda and V.L. Patel were associated w i t h the work. 3. Data. Data from Wilkes and Thule were reduced according to the CSAGI plan and submitted to the IGY World Data Centers. 4. Results. a. Large seasonal v a r i a t i o n s of cosmic-ray i n t e n s i t y i n polar regions were found from the data of Wilkes and Thule telescopes, which were corrected f o r barometric e f - f e c t by the c o e f f i c i e n t s determined by regression analysis. I n t e r p r e t a t i o n of t h i s seasonal v a r i a t i o n by atmospheric temperature e f f e c t s as w e l l as t h e o r e t i c a l explana- t i o n f o r the anormally large values of temperature c o e f f i c i e n t s f o r those polar s t a - t i o n s were discussed and published. b. I n v e s t i g a t i o n of solar f l a r e e f f e c t on the cosmic-ray i n t e n s i t y i n polar r e - gions was performed by making use of Wilkes and Thule data. The r e s u l t s showed a r e - markable f a c t , i n d i c a t i n g the h i g h l y disturbed nature of the i n t e r p l a n e t a r y f i e l d during IGY. This r e s u l t and an i n t e r p r e t a t i o n of the c o n t r o v e r s i a l r e s u l t s of solar f l a r e e f f e c t on cosmic-ray i n t e n s i t y among several i n v e s t i g a t o r s were published. c. From the analyses of high counting r a t e cosmic-ray data obtained at the moun- t a i n s t a t i o n s (Climax and B a n f f ) , a strong l o c a l time dependence of short period f l u c - t u a t i o n s was detected. Further i n v e s t i g a t i o n s of these r a p i d f l u c t u a t i o n s are s t i l l i n processing. d. On May 4, 1960 a ra p i d increase i n cosmic-ray i n t e n s i t y was observed at v a r i - ous s t a t i o n s i n the world. The rate-meter records at Climax, Banff, and College Park and 15 minute data of mu-meson telescope at Thule gave valuable i n f o r m a t i o n on t h i s event. D e t a i l s are now being published. 5. Bibliography. a. Papers Presented at Meetings. V.L. Patel and K. Maeda: "Seasonal V a r i a t i o n of Cosmic Ray I n t e n s i t y i n Polar Regions." January 27, 1960 Annual Meeting of Am. Phys. Soc. b. Published Papers. V.L. Patel and K. Maeda: "Short-term V a r i a t i o n s i n Meson and Nucleon Compon- ent of Cosmic Rays." JGR. v o l . 66, no. 4, A p r i l 1961. K. Maeda and V.L. Pa t e l : "Note on Solar Flare Cosmic Rays." JGR, v o l . 66, no. 4, A p r i l 1961. K. Maeda and V.L. Pa t e l : "Seasonal Var i a t i o n s of Cosmic Ray I n t e n s i t y i n Polar Regions." JGR, v o l . 66, no. 5, May 1961. S.F. Singer, K. Maeda, and V.L. Patel: "Solar Flare Cosmic Ray on May 4, 1960." JGR. v o l . 66, no. 5, May 1961. 120

COSMIC RAYS Project 2.33 - Cosmic-Ray Tr a j e c t o r y Computation and Study 1. Objectives. At the time t h i s p r o j e c t at the School of Physics, U n i v e r s i t y of Min- nesota, was begun a number of cosmic ray measurements had shown that the cosmic-ray i n t e n s i t y as a f u n c t i o n of p o s i t i o n on the earth's surface was q u i t e d i f f e r e n t from that predicted by a theory which approximated the earth's magnetic f i e l d by that of a magnetic di p o l e . This p r o j e c t was undertaken to see whether these deviations from p r e d i c t i o n were due to the inaccurate model assumed f o r the earth's magnetic f i e l d or whether they i n d i c a t e d a misunderstanding about magnetic f i e l d s i n space. 2. Operations. An e l e c t r o n i c computer was used to c a l c u l a t e a number of o r b i t s or charged p a r t i c l e s using b e t t e r approximations to the earth's f i e l d . 3. Personnel. This work was c a r r i e d out by Paul J. Kellogg, Melvin Schwartz and Robert Tennison. 4. Results. The f i r s t phases of the work were c a r r i e d out using a 15 parameter ap- proximation to the earth's f i e l d . The r e s u l t s showed b e t t e r agreement w i t h cosmic-ray observations than previous c a l c u l a t i o n s , but l e f t some discrepancy. Kellogg then car- r i e d out c a l c u l a t i o n s using a 48 parameter approximation to the earth's magnetic f i e l d which was the best a v a i l a b l e and showed th a t a l l cosmic-ray observations w i t h i n about 15° of the magnetic equator agreed p e r f e c t l y w i t h the r e s u l t s of the c a l c u l a t i o n s . I t proved i m p r a c t i c a l w i t h the computer a v a i l a b l e to compute t r a j e c t o r i e s f o r l a t i - tudes near the earth's magnetic poles. 5. Bibliography. P.J. Kellogg and M. Schwartz: "Theoretical Study of the Cosmic Ray Equator." I I Nuovo Cimento. Serie X, v o l . 13, pp. 761-768, Aug. 1959. P.J. Kellogg: "Calculations of Cosmic-Ray T r a j e c t o r i e s Near the Equator." JGR, v o l . 65, no. 9, Sept. 1960. 121

COSMIC RAYS Project 2.34 - Reduction of Cosmic-Ray I o n i z a t i o n Chamber Data 1. Obiectives. This p r o j e c t at the Department of T e r r e s t r i a l Magnetism, Carnegie I n s t i t u t i o n of Washington, provided f o r s c a l i n g , reduction, and p u b l i c a t i o n of pres- sure corrected b i - h o u r l y values f o r the d u r a t i o n of the IGY (J u l y 1957 t o December 1958) from cosmic-ray i o n i z a t i o n chambers at Godhavn and Mexico i n conformity w i t h CSAGI recommendations. I n aCddition, i t was planned to scale, reduce, and p u b l i s h pressure-corrected data from Godhavn f o r the period January 1951 to July 1957. 2. Operations. Data from the s t a t i o n s involved were c o l l e c t e d at DTM and corrected f o r bursts and barometric pressure. Tables of b i h o u r l y means of departure from b a l - ance, d a i l y means of hourly departures from balance, and b i h o u r l y values of d i u r n a l v a r i a t i o n s i n departure from balance, were prepared. The data f o r Godhavn and f o r Mexico are included i n a Carnegie I n s t i t u t i o n of Washington p u b l i c a t i o n now i n p r i n t (see Bibliography below). 3. Personnel. These tables and reductions were ef f e c t e d by L i s e l o t t e Beach w i t h t e c h n i c a l assistance by S.E. Forbush. 4. Results. The 24-hour and 12-hour waves i n cosmic-ray i n t e n s i t y at Cheltenham (Fredericksburg), Huancayo, and Christchurch and t h e i r v a r i a b i l i t y were analyzed s t a - t i s t i c a l l y , using data, corrected f o r pressure, f o r the period 1937-1959 from Compton- Bennett i o n i z a t i o n chambers. The degree of c o r r e l a t i o n between the deviations of yearly mean 24-hour waves (from t h e i r 23-year means) at any two of the s t a t i o n s i s almost as great as can be expected when account i s taken of the noise l e v e l inherent i n the instruments. The deviations of ye a r l y means, from t h e i r 23-year averages, i n - dicate large secular v a r i a t i o n s which may be due to a quasi-systematic 22-year v a r i a - t i o n . The phase di f f e r e n c e between these yearly d e v i a t i o n vectors at Huancayo and Cheltenham (or Christchurch) i s considerably less than that between the average vec- to r s f o r 23 years. The s t a t i s t i c a l r e a l i t y of the 12-hour wave i s d e f i n i t e l y estab- lished at a l l three s t a t i o n s , although, at least at Huancayo, the average 12-hour wave probably r e s u l t s e n t i r e l y from systematic e r r o r s due to exceedingly small f r i c - t i o n a l e f f e c t s i n the barograph. 5. Bibliography. S.E. Forbush, D. Venkatesan. "Diurnal V a r i a t i o n i n Cosmic-Ray I n t e n s i t y 1937-59, at Cheltenham (Fredericksburg), Huancayo, and Christchurch." JGR. v o l . 65, no. 8, August 1960, pp. 2213-26. L i s e l o t t e Beach, S.E. Forbush: "Cosmic-Ray Results." Res, of the Dept. of Terrest. Magnetism. Carnegie I n s t i t u t i o n of Washington. 122

COSMIC RAYS Project 2.35 - Airborne Neutron Monitor Survey of the Geomagnetic Equator 1. Objectives. This p r o j e c t was work contributed to the IGY program by the A i r Force Cambridge Research Laboratories (AFCRL), and the U n i v e r s i t y of Chicago (sponsored under USAF O f f i c e of S c i e n t i f i c Research and AFCRL c o n t r a c t s ) . The purpose was to obtain crossings of the geomagnetic equator at longitudes spaced around the earth i n order to map the p o s i t i o n of the cosmic-ray minimum. Since the cosmic rays begin to i n t e r a c t w i t h the earth's magnetic f i e l d throughout a large volume at a considerable distance from the e a r t h , some of the nature of the f i e l d i n these remote regions can be deduced. 2. Operations. Through the cooperation of the A i r Force, a nucleonic component mon- i t o r (two detector, Chicago design) was i n s t a l l e d i n a long-range a i r c r a f t and trans- ported at constant pressure a l t i t u d e (approximately 18,000 f e e t ) i n a p a t t e r n of traverses across the equator; twelve traverses were obtained f o r which the data can be analyzed to give the shape of the curve both sides of minimum (see Fig. 8 ) . 3. Personnel. Ludwig Katz, AFCRL, and J.A. Simpson, U n i v e r s i t y of Chicago, were pro- j e c t supervisors. 4. Data. The reduced data were published as part of the papers r e p o r t i n g on t h i s work. Some of the data reduction was c a r r i e d out under a special research p r o j e c t supported by the USNC w i t h funds from the Ford Foundation. 5. Results. The cosmic-ray equator was found to l i e west of the equator computed from the eccentric dipole approximation of the earth's magnetic f i e l d (see Fig. 9 ) . Agreement i s b e t t e r w i t h the surface dip equator, although i t can be seen that the A t l a n t i c Ocean anomaly i n the v i c i n i t y of 60°W Longitude apparently does not s i g n i f i - c a n t ly a f f e c t the cosmic-ray d e f l e c t i o n . These studies on the cosmic-ray equator, which o r i g i n a t e d at Chicago, have led to worldwide changes i n the geomagnetic c u t - o f f s f o r charged p a r t i c l e s a r r i v i n g at the earth. The work has stimulated many i n v e s t i g a t i o n s both i n the U.S. and Europe. I n a d d i t i o n to the cosmic-ray equator, the f i r s t d e f i n i t e measurement of the lon- gitude e f f e c t of cosmic r a d i a t i o n at the geomagnetic equator was obtained i n these experiments, which independently show that the magnetic center i s eccentric w i t h r e - spect to the earth's axis of r o t a t i o n . 6. Bibliography. J.A. Simpson: "New Experiments Concerning the Geomagnetic F i e l d Extending i n t o I n t e r p l a n e t a r y Space." Geophys. Monog. No. 2, Geophysics and the ICY, pp. 65-70, Am. Geophys. Union, 1958. L. Katz, P. Meyer, J.A. Simpson: "Further Experiments Concerning the Geomag- ne t i c F i e l d E f f e c t i v e f o r Cosmic Rays." Nuovo Cimento. Suppl. a l v o l . V I I I , Ser. X, no. 2, 1958. 123

COSMIC RAYS 120 ISO 180 1M m Center Eqiiatori Ecdentrk Rhasi 190 130 90 60 Figure 8. Route of A i r c r a f t Carrying Neutron Monitor a t Constant Pressure A l t i t u d e . 20»(^^ f 030" ho»A/ - Cosmic Ray Equator Eccentric Dipole Held Equator Dip Equator(O'^lnclination) "'1945 Survey West ± 0E06RAPHIC LONGITUDE <P f^^^ jo* Sjô 'liô 'is^ 'eo"' 'if' ' ly' 'i^ 'ii^ 'ijoi" Sjd̂ telr -ho»s Figure 9. Comparison of Cosmic Ray, Dipole and Dip Equators. 124

I l l GEOMAGNETISM PROGRAM Askania E a r t h Variograph

GEOMAGNETISM PROGRAM Page A. Organization of Technical Panel on Geomagnetism 127 B. Summary of Panel Actions 127 C. Project Objectives and Results 129 3.1 Geomagnetism Headquarters, Data Reduction & P u b l i c a t i o n 130 3.2, 3.13, 3.14 - Operations of Magnetic Observatories i n the A n t a r c t i c 131 3.3 Guam - Koror Magnetic Observatories 132 3.4 East-West Network o f Magnetic Recording Stations 133 3.5 North-South Network (Alaska) of Magnetic Recording Stations. . . . 134 3.6, 3.7 - Magnetic Gradient Studies i n Alaska 135 3.8 Operations of Rapid-Rtin A u x i l i a r y Magnetographs 136 3.9 Single Component V i s i b l e Recording Magnetographs 136 3.10 Sub-Audio-Frequency Geomagnetic Fluctuations 137 3.11 Magnetic Observations a t J a r v i s , Palmyra and Fanning 140 3.12, 3.15, 3.17 - Equipment f o r Magnetic Stations a t J a r v i s , Palmyra, Fanning, A r c t i c Ice Floe ( S t a t i o n A ) , and the South American 5-Station Network 141 3.16 Equatorial E l e c t r o j e t i n Peru 142 126

I I I . GEOMAGNETISM PROGRAM A. Organization of Technical Panel on Geomagnetism 1. Establishment of Panel: L e t t e r s were w r i t t e n I n December 1954 - January 1955 t o nominees f o r panel membership, M, A, Tnve was asked t o convene the f i r s t meeting, a t which E. 0. Hulbnrt was elected Chairman, and E, B. Roberts, Secretary. The panel recommended t h a t R. R, Revelle be I n v i t e d to become a member I n order t o e f f e c t l i a i - son w i t h the panel on oceanography. Chairman. L a t e r , E. B. Roberts was designated as Vlce- 2, Composition of the Panel. ( A f f i l i a t i o n a t time of appointment.) a. Panel Members Leroy R. Alldredge, Walter M. Elsasser Edward 0. Halburt Roger R. Revelle E l l i o t t B. Roberts Merle A. Tuve V i c t o r Vacquler E. H. Vestlne Naval Ordnance Laboratory U n i v e r s i t y of Utah Chairman - r e t i r e d ( D i r e c t o r S c i e n t i f i c Research, NKL) Scrlpps I n s t i t u t i o n of Oceanography Vice-chairman: U. S. Coast and Geodetic Survey Carnegie I n s t i t u t i o n of Washington, De- partment of T e r r e s t r i a l Magnetism New Mexico I n s t i t u t e o f Mining and Tech- nology Carnegie I n s t i t u t i o n of Washington, De- partment of T e r r e s t r i a l Magnetism b. Consultants Walter S. McAffee, J r . John McClay A, G. McNlsh J. H. Nelson U. S. Army Signal Research, and Development Laboratory Geophysics Research Center (AFCRC) National Bureau of Standards U. S. Coast and Geodetic Survey c. S e c r e t a r i a t (IGY S t a f f ) G. F. S c h i l l i n g ( t o May 1955) Stanley Ruttenberg (from May 1955) 3. Panel Meetings. Four meetings of the panel were held I n the period 1955-1956, F i r s t Meeting Second Meeting Thi r d Meeting Fourth Meeting January 24, 1955 February 14, 1955 May 5, 1955 May 15, 1956 Washington, D, C, Washington, D. C, Washington, D, C, Washington, D, C. ^ B. Summary of Panel Actions 1. Working Groups. A group was appointed (Drs. Vacquler, Vestlne, McNlsh) t o study the p o s s i b i l i t y of budgeting f o r a program of analysis and research on IGY data I n geomagnetism, p a r t i c u l a r l y w i t h reference t o I n t e r d i s c i p l i n a r y problems. E. H. Vestlne and J. H, Nelson were asked t o study the question of chains of 127

GEOMAGNETISM sta t i o n s I n western United States and Alaska, and of spe c i a l observations I n Alaska t o o b t ain gradients, 2. O r i g i n a l Program. Following CSAGI recommendations, a program of determining f i n e s t r u c t u r e o f t r a n s i e n t phenomena was planned I n Alaska, where two s t a t i o n s would be established about 100 miles from College to form a t r i p a r t i t e network. A d i f f e r e n - t i a l magnetograph was being designed f o r I n s t a l l a t i o n a t College; the 5-10 mile spac- ing between elements was expected t o give Information on magnetic f i e l d g r a d i e n t s , p a r t i c u l a r l y during magnetic storms. Rapid-run Instruments were t o be I n s t a l l e d a t a number of st a t i o n s t o study the higher frequency f l u c t u a t i o n s . Two s t a t i o n s were planned i n the A n t a r c t i c and several l o c a t i o n s I n the P a c i f i c near the magnetic equa- t o r were suggested as possible s i t e s f o r new observatories. 3. A n t a r c t i c Program. As plans f o r the U. S. program enlarged. I t was decided t o I n s t a l l several new st a t i o n s I n the A n t a r c t i c . The Panel studied the equipment needs f o r these s t a t i o n s and came to the conclusion t h a t I t was not necessary t o have abso- l u t e measurements a t a l l s t a t i o n s a t a l e v e l t h a t would be considered necessary f o r permanent-tjrpe s t a t i o n s . The savings thus e f f e c t e d could be used t o strengthen the study of the f l u c t u a t i o n s and t r a n s i e n t phenomena. Later I n the planning phase I t was decided t h a t I t might be very desirable t o I n s t i t u t e a new program I n South Amer- ica (see discussion below). I n order t o f i n d funds t o meet the expense of t h i s pro- gram I t was decided t o eli m i n a t e magnetic measurements from one of the a n t a r c t i c s t a - t i o n s . I t was ascertained from the B r i t i s h IGY Committee t h a t magnetic measurements were t o be Included I n the program a t the B r i t i s h s t a t i o n a t Halley Bay, which would only be one hundred miles from the proposed U. S, s t a t i o n a t the Weddell Sea ( E l l s - w o r t h ) , I t was therefore decided t o recommend t h a t the magnetic program be cancelled a t E l l s w o r t h , 4. Close Spaced Chains of Stations. Early i n the program i t was recognized t h a t obser- vations from a chain of st a t i o n s might provide valuable Information on magnetic storm phenomena. Preliminary budgetary considerations, however, precluded the planning of such s t a t i o n s . As the budget was Increased f o r the U. S. program, i t was then found possible to Include such experiments. The working group, c o n s i s t i n g of Dr. E. H. Vestine and Mr. J. H. Nelson, studied the p o s s i b i l i t i e s of such experiments and rec- ommended t h a t two chains of s t a t i o n s be planned. a. North-South Chain I n Alaska. Five locations were recommended I n Alaska; each s t a t i o n would have a three-component Askanla Varlograph I n s t a l l e d I n a pr e f a b r i c a t e d nonmagnetic s h e l t e r and serviced from the main observatory a t College. b. Western United States. I n order t o study the morphology of m l d - l a t l t u d e of geomagnetic disturbances. I t was recommended t h a t an east-west chain of s t a t i o n s be operated I n Western United States w i t h spacing of approximately 300 kilome t e r s . Five locations were selected where normal s e n s i t i v i t y Askanla Varlographs could be I n s t a l l e d i n p r e fabricated nonmagnetic s h e l t e r s . Two other s t a t i o n s were selected t o give a short north-south cross arm. 5. P a c i f i c Program. Early planning c a l l e d f o r s t a t i o n s near the magnetic d i p equa- t o r i n the Eastern and Western P a c i f i c . A f t e r plans of other nations were ascertained and i n conjunction w i t h other U. S. programs, p a r t i c u l a r l y oceanography. I t was de- cided t o organize a t h r e e - s t a t i o n network of s t a t i o n s I n the Line Islands I n the East- ern P a c i f i c t o be undertaken by the Scrlpps I n s t i t u t i o n of Oceanography, U n i v e r s i t y of C a l i f o r n i a , I t was also f i n a l l y decided t o i n s t a l l two s t a t i o n s a t Guam and Koror i n the Western P a c i f i c , 6. A r c t i c Program. When plans were developed by the U. S. National Committee f o r s c i e n t i f i c s t a t i o n s i n the A r c t i c Basin, e i t h e r on a f l o a t i n g Ice i s l a n d (T-3) or a s t a t i o n on the pack i c e , i t was decided t h a t one of these s t a t i o n s might be a u s e f u l 128

GEOMAGNETISM l o c a t i o n f o r a magnetograph. I t was decided t o put the magnetograph a t S t a t i o n A, which would be located several hundred miles n o r t h of Barrow, Alaska, on the pack I c e . Absolute measurements were not provided f o r Inasmuch as t h i s s t a t i o n would not remain f i x e d but would d r i f t and r o t a t e under the movement of the pack I c e , 7, High Freqtiency Geomagnetic Studies. There were suggestions I n the e a r l y phases of the planning t o extend the frequency range of studying t r a n s i e n t phenomena to d i s - turbances w i t h periods of one second t o a few hundredths of a second, i n other words, i n the subaudio frequency range. Dr. Leroy Alldredge and Elwood Maple prepared a pro- posal f o r the Panel. Discussions were also held w i t h other i n t e r e s t e d i n v e s t i g a t o r s such as R. E. Holzer, I n s t i t u t e of Physics, U n i v e r s i t y of C a l i f o r n i a , Los Angeles, and a proposal was also examined from Dr. A. R. Jordan, Denver Research I n s t i t u t e , U n i v e r s i t y of Denver. I t was f i n a l l y decided t h a t a program undertaken by the Geo- physics Research D i r e c t o r a t e under the supervision of Elwood Maple i n cooperation w i t h the Denver Research I n s t i t u t e would be recommended. Dr. Holzer having withdrawn h i s proposal i n view of other commitments. This program would con s i s t of f i v e s t a t i o n s a t various magnetic l a t i t u d e s w i t h slow-speed tape recorders, s p e c i a l l y designed low- noise a m p l i f i e r s and oriented magnetic c o i l s as sensing elements. 8, V i s u a l Recording Program. The Geomagnetism Panel was asked by the Technical Panel on Ionospheric Physics t o look i n t o the f e a s i b i l i t y of providing some d i r e c t reading magnetometers f o r p a t r o l purposes a t selected ionospheric s t a t i o n s . Several types of equipment were te s t e d , i n c l u d i n g a commercially a v a i l a b l e vacuum tube s e n s i t i v e t o ambient magnetic f i e l d s . The Coast and Geodetic Survey f i n a l l y made recommendations as t o the most s u i t a b l e types of Instruments and, under a p r o j e c t approved by the Panel, furnished them f o r operation a t locations selected by the Ionospheric Physics Panel. 9, Data Redxiction and P u b l i c a t i o n . I n response t o CSAGI recommendations developed a t the Rome meeting, the Panel discussed the needs f o r various types of data reduction and the exchange of data i n the geomagnetism program. Several schemes f o r the p u b l i - c a t i o n of selected data from the geomagnetic s t a t i o n s were also discussed. The Panel accepted the r e p o r t of the Coast and Geodetic Survey on the f e a s i b i l i t y of publishing magnetograms and hourly values as s t a t i o n books i n the number of about 500 copies f o r the U. S. s t a t i o n s . A t the time of t h i s Panel a c t i o n , the number of U. S. st a t i o n s was 8; l a t e r budgetary expansion of the program approximately doubled the number of sta t i o n s and i t proved t o be possible t o give complete p u b l i c a t i o n t o only a selected number of s t a t i o n s . F t i b l l c a t l o n of l i m i t e d i n f o r m a t i o n was then planned f o r the r e - maining s t a t i o n s . C. Proje c t Objectives and Results 1. Summary of Program. The geomagnetic program consisted of a series of experiments mainly designed t o y i e l d f a c t s about the magnetic f i e l d f l u c t u a t i o n s which a r i s e from influences e x t e r n a l t o the surface of the e a r t h . Projects provided f o r the procure- ment, i n s t a l l a t i o n and operation of geomagnetic equipment i n several new s t a t i o n s and f o r the operation, c o l l e c t i o n and analysis of data from new and e x i s t i n g geomagnetic s t a t i o n s . 2, Order of Pr o j e c t D e s c r i p t i o n . The p r o j e c t s t h a t are described i n the f o l l o w i n g pages are i n ntimerlcal order t o correspond w i t h the o r i g i n a l f ormulation of the pro- gram, w i t h the exception t h a t a few c l o s e l y r e l a t e d p r o j e c t s are grouped together. 129

GEOMAGNETISM Project 3.1 - Geomagnetism Headquarters, Data Reduction and P u b l i c a t i o n 1. Objectives, a. F i e l d Operations, This p r o j e c t , a t the U, S. Coast and Geodetic Survey, provided f o r the operations headquarters f o r a l l of the geomagnetism p r o j e c t s under- taken by the Coast and Geodetic Survey f o r the IGY, U t i l i z i n g the f a c i l i t i e s of the Fredericksburg Magnetic Observatory, instruments were t e s t e d , c a l i b r a t e d and stan- dardized. I n a d d i t i o n , observers f o r the new st a t i o n s were t r a i n e d f o r the operation and maintenance of instruments. S t a f f members of the Geomagnetism Branch, Geophysics D i v i s i o n , USCGS, assisted i n i n s t a l l a t i o n of instruments a t new locations and made v i s i t s during the course of the IGY to many s t a t i o n s i n order to assure u n i f o r m i t y of techniques and to a s s i s t i n solving problems a r i s i n g w i t h f i e l d operations. b. Data Reduction and P u b l i c a t i o n , The Survey supervised the reduc t i o n of mag- netograms taken during the IGY which consisted of ( i ) the scali n g of mean hourly or- dinates of the three vector components recorded on standard magnetograms, ( i i ) con- v e r t i n g the ordinates to gammas (or minutes of arc) by a p p l i c a t i o n of scale-value fac- t o r s , and ( i i i ) the a d d i t i o n of base-line values, where possible, to the hourly values to y i e l d tables of absolute hourly means. Steps ( i i ) and ( i i i ) required a s u b s t a n t i a l amount of study and analysis of the records from each s t a t i o n t o insure the adoption of the most s a t i s f a c t o r y scale values and base l i n e s , 2. Operations, Data from 7 IGY observatories ( L i t t l e America, Byrd, Wilkes, Koror, Guam, Healy, Big Delta) have been published i n booklet form patterned a f t e r the reg- u l a r observatory p u b l i c a t i o n s of the Coast and Geodetic Survey, These books include tables of hourly-values and reproductions of a l l normal-speed n o r m a l - s e n s i t i v i t y mag- netograms. Four a d d i t i o n a l IGY recording s t a t i o n s ( J a r v l s I s l a n d , Fanning I s l a n d , B e l o i t , Anchorage) were treated by p u b l i c a t i o n of hourly-value tables but without reproductions of magnetograms. Some processing of hourly-value tables was done f o r eleven more recording s t a t i o n s (Barter I s l a n d , Kotzebue, For t Yukon, Northway, H a l l e t t , P r i c e , Casper, L e a d v i l l e , Espanola, B u r l i n g t o n , C a r r o l l t o n ) but without p u b l i c a t i o n ; the r e s u l t s are a v a i l a b l e on m i c r o f i l m f o r workers who require these data. The book- l e t s were p r i n t e d i n l i m i t e d q u a n t i t y and d i s t r i b u t e d n a t i o n a l l y and i n t e r n a t i o n a l l y t o research organizations and s c i e n t i s t s known to be i n t e r e s t e d , and have been sub- mit t e d also 'to the World Data Centers. For data not published microfilms were sup- p l i e d to the World Data Centers. 3. Personnel. The general program of the Coast and Geodetic Survey was under the supervision of E. B. Roberts, Chief, Geophysics D i v i s i o n , and J. H. Nelson, Chief, Geomagnetism Branch. Mr. Joel B. Campbell served as the Survey's IGY operations o f f i c e r . The processing of data was under the supervision of Kendall Svendsen and John Gettemy, 130

GEOMAGNETISM Projects 3,2, 3,13 and 3.14 - Operation of Magnetic Observatories i n the A n t a r c t i c 1. Obiectives. These p r o j e c t s of the U. S. Coast and Geodetic Survey provided f o r i n s t a l l a t i o n of standard magnetic observatories a t U. S. s t a t i o n s i n the A n t a r c t i c and f o r operation of t h i s equipment during the IGY. I n a d d i t i o n t o the a c q u i s i t i o n of data f o r the purposes of studying phenomena of the magnetic f i e l d I t s e l f , i . e . , the absolute value of the f i e l d and i t s changes and magnetic storms, these p r o j e c t s were part of a broad program i n v o l v i n g the c o r r e l a t i o n of data from many d i s c i p l i n e s , i n c l u d i n g ionospheric physics, aurora and cosmic rays. 2. Operations. Equipment was i n s t a l l e d a t L i t t l e America, Byrd S t a t i o n , Amundsen- Scott (South Pole) S t a t i o n , Wilkes S t a t i o n , and, i n cooperation w i t h New Zealand, Cape H a l l e t t S t a t i o n . New Zealand s c i e n t i s t s operated the equipment a t Cape H a l l e t t and U. S. observers are responsible f o r operations a t the other A n t a r c t i c Stations. The instrtmientatlon a t L i t t l e America, Byrd and Wilkes Stations was tha t of a standard magnetic observatory, w i t h normal-speed and rapid-run records of the vector changes of the f i e l d , and w i t h regular absolute c a l i b r a t i o n s f o r c o n t r o l of variometer performance and f o r determination of secular change. Equipment a t Cape H a l l e t t and at the Pole S t a t i o n consisted of a 3-component Askania Variograph, 3. Personnel. This p r o j e c t was under the general supervision of E, B. Roberts, J. H. Nelson and Joel B. Campbell. 4. Data. Data have been processed and published according to CSAGI recommendations as discussed under Project 3.1. A l l IGY A n t a r c t i c data have been submitted to the data centers. 5. Results, As these were p r i n c i p a l l y data c o l l e c t i n g p r o j e c t s , r e s u l t s are d i s - cussed elsewhere (Projects 22.13 and 50.1). 131

GEOMAGNETISM Project 3.3 - Guam - Koror Magnetic Observatories 1. Obiectives. Ntnnerous scattered observations over a period of a number of years had ind i c a t e d a region near the magnetic dip equator of special geomagnetic s i g n i f i - cance — the locus of the postulated " e q u a t o r i a l e l e c t r o j e t . " Questions had a r i s e n , moreover, as t o the r e l a t i o n s between the e l e c t r o j e t and the geographic equator, the geomagnetic equator, and the magnetic d i p equator. Koror was chosen by the U. S, Coast and Geodetic Survey as one of the nearest possible s i t e s t o the d i p equator. (Later f i e l d measurements near the Koror observatory i n d i c a t e d the ob j e c t i v e of loca- t i o n had been achieved w i t h remarkable accuracy, f o r the p o s i t i o n of the eqtiator i t - s e l f was found t o be probably less than ten miles from the observatory.) A t t h i s p o i n t there was appreciable separation of the three "equators," the geographic l a t i - tude of the s t a t i o n being 7° 20' North, and the geomagnetic l a t i t u d e 3.2° South. The s i t e a t Guam was chosen as a c o n t r o l s t a t i o n f o r Koror, being f a r enough away t o res- pond very l i t t l e t o the e f f e c t s of the e l e c t r o j e t . 2. Operations. Prefabricated non-magnetic alxminum b u i l d i n g s were erected f o r the recording Instruments and f o r the absolute c a l i b r a t i o n instruments. L i v i n g quarters were b u i l t on Koror but on Guam were made a v a i l a b l e through the cooperation of the National Bureau of Standards. Instrumentation a t both observatories was t h a t of a f i r s t - c l a s s standard magnetic observatory, w i t h f u l l absolute c o n t r o l of base-line values, and w i t h standard-speed and rapid-run magnetographs of normally high s e n s i t i v i t y . 3. Personnel. The p r o j e c t was under the general supervision of E. B. Roberts, J. H. Nelson, and Joel B. Campbell. 4. Data. Data have been processed and published, or are a v a i l a b l e on m i c r o f i l m as discussed under Project 3.1. A l l data from the IGY period have been submitted to the data centers, 5. Results. While t h i s was p r i n c i p a l l y a data c o l l e c t i n g p r o j e c t , some study of the enhancement of daytime a c t i v i t y and the range of d i u r n a l v a r i a t i o n a t Koror has been made by s c i e n t i s t s of the Survey and copies of records have been furnished t o other i n v e s t i g a t o r s f o r a n a l y s i s . Since the IGY, the magnetic observatory a t Guam has been continued by the Coast and Geodetic Survey as a permanent part of regular f i e l d operations. 6. Bibliography. Knapp, David G.: "Some IGY Geomagnetic Results m the P a c i f i c , and a Suggestion as t o the O r i g i n of the Equatorial E l e c t r o j e t . " (Processed), U, S, Coast and Geodetic Survey, 1958, 9 pp. Gettemy, John W.. "Magnetic Daily V a r i a t i o n a t Koror." Joum. Geophys. Res., v o l . 67, 1962, pp. 1885-1888. Knapp, David G., John W. Gettemy: "A New Longitude E f f e c t i n the Geomagnetic Solar D a i l y V a r i a t i o n . " Joum. Geophys. Res., v o l . 68, 1963, pp. 2411-2420. 132

GEOMAGNETISM Proj e c t 3,4 - East-West Network of Magnetic Recording Stations 1, Objectives, Inasmuch as there had been some I n t e r e s t during the past decade or so i n possible c o r r e l a t i o n between geomagnetic a c t i v i t y and meteorological changes— possibly through mass movement of atmospheric " c e l l s " and possible d i f f e r e n t i a l i o n i - z a t i o n i n the high atmospheres—it was expected t h a t the east-west chain of magnetic recorders I n s t a l l e d by the U. S, Coast and Geodetic Survey would y i e l d magnetic data u s e f u l i n such studies. 2, Operations. Five magnetic recording s t a t i o n s were i n s t a l l e d on an east-west l i n e approximately 350 kilometers apart a t L e a d v i l l e , Colorado; B u r l i n g t o n , Colorado; P r i c e , Utah; B e l o l t , Kansas; C a r r o l l t o n , Missouri; i n a d d i t i o n , two other s t a t i o n s , Espanola, New Mexico, and Casper, Wyoming, provided a short north-south i n t e r s e c t i n g l i n e . The s t a t i o n s were equipped w i t h Askania Variographs, a semi-portable 3-component magnetic recorder. Because the instruments were a r e l a t i v e l y new type, there was of t e n d i f f i c u l t y i n securing s a t i s f a c t o r y continuous operation, and the p r e c i s i o n of time marking on the magnetograms was sub-standard because of non-uniform f i l m speed. I n s p i t e of these d i f f i c u l t i e s , however, recordings of considerable value were ob- tained. The instrtmients were l e f t unattended i n s p e c i a l l y constructed shelters and were serviced p e r i o d i c a l l y t o remove records, replace f i l m , and make adjustments i n c a l i - b r a t i o n s , e t c , 3, Personnel, The p r o j e c t was under the supervision of E, B, Roberts, J, H. Nelson and Joel B, Campbell, 4, Data, Data have been processed, published, or are a v a i l a b l e on m i c r o f i l m as d i s - cussed under Project 3,1, A l l IGY data have been supplied t o the data centers, 5, Results, Records from t h i s p r o j e c t have been furnished t o research s c i e n t i s t s and s i g n i f i c a n t papers were published i n the s c i e n t i f i c l i t e r a t u r e concerning magnetic storms and magnetic e f f e c t s of high a l t i t u d e nuclear explosions i n the P a c i f i c (actu- a l l y not part of the IGY program). 133

GEOMAGNETISM Project 3.5 - North-South Network (Alaska) of Magnetic Recording Stations 1. Obiectives, The o r i g i n a l i n t e n t of the north-south array of magnetic recording s t a t i o n s i n s t a l l e d by the U. S, Coast and Geodetic Survey was to supplement the three standard Alaskan magnetic observatories — Barrow, College, and Sitka — i n obtaining a general coverage of v a r i a t i o n s of the geomagnetic f i e l d i n and across the a u r o r a l zone. This would permit the p o s t u l a t l o n and study of e l e c t r i c currents i n the iono- sphere t h a t would cause or be associated w i t h the observed vector changes i n the mag- n e t i c f i e l d , leading t o b e t t e r understanding of a l l the r e l a t e d phenomena i n c l u d i n g a u r o r a l a c t i v i t y , ionospheric physics, cosmic rays, and space f i e l d s i n general. 2. Operations. Each recording s t a t i o n consisted of a 3-component Askania Variograph I n s t a l l e d i n a prefabricated non-magnetic aluminum instrtmient s h e l t e r . I n s t a l l a t i o n s were made a t Barter I s l a n d , Kotzebue, Fort Yukon, Anchorage, Northway. I n general, the performance of the instruments was reasonably good, although the non-uniformity of f i l m speed l e f t soiriething to be desired i n the way of precise time c o n t r o l on the records. 3. Personnel. The p r o j e c t was under the supervision of E, B. Roberts, J. H. Nelson and Joel B. Campbell. 4. Data. Data have been processed, published, or are ava i l a b l e on mi c r o f i l m s , as discussed under Project 3,1, A l l IGY data have been supplied t o the data centers. 5. Results, Considerable study of the r e s u l t i n g records, together w i t h other Alaskan magnetic records, has been made by the Geophysical I n s t i t u t e of Alaska and by scien- t i s t s of the Coast and Geodetic Survey, 134

GEOMAGNETISM Projects 3.6 and 3.7 - Magnetic Gradient Studies i n Alaska 1. Objectives, Although established as separate p r o j e c t s by the U. S. Coast and Geodetic Survey, f o r a d m i n i s t r a t i v e reasons, these two IGY a c t i v i t i e s should be con- sidered as parts of the same p r o j e c t , both c l o s e l y r e l a t e d t o the Alaskan North-South Network of magnetic recording s t a t i o n s . P r i m a r i l y , the College-Big Delta-Healy i n - s t a l l a t i o n was intended f o r gradient studies of the geomagnetic f i e l d . Two sets of t r i p a r t i t e s t a t i o n s were expected to y i e l d data t h a t would permit the more precise d e s c r i p t i o n of e l e c t r i c currents i n the ionosphere associated w i t h disturbances i n the magnetic f i e l d . 2. Operations. The Healy and Big Delta locations were equipped w i t h f i r s t - c l a s s magnetographs f u l l y equivalent t o those a t the College observatory — normal- and l o w - s e n s i t i v i t y recorders employing standard recording speed, and a rapid-run magneto- graph. Healy i s approximately on the same geomagnetic meridian w i t h College, Big Delta approximately on the same geomagnetic p a r a l l e l of l a t i t u d e ; both a u x i l i a r y sta- t i o n s were about 130 kilometers from College. (During the e a r l y planning phases the southern a u x i l i a r y s t a t i o n was r e f e r r e d to as McKinley Park. The a c t u a l s i t e chosen was a t Healy.) Prefabricated non-magnetic aluminum b u i l d i n g s were used to house the recording instruments and provide a she l t e r f o r absolute c a l i b r a t i o n measurements a t Healy and Big Delta. A d i f f e r e n t i a l magnetograph, i n s t a l l e d i n two outpost shelters some 10 kilometers to the magnetic south and west of the main c o n t r o l equipment a t College and connected by cable w i t h the College Observatory, was designed to record differences between changes i n the magnetic vector a t the outpost s i t e s and a t the observatory. 3. Personnel. The p r o j e c t was under the supervision of E. B. Roberts, J. H. Nelson and Joel B. Campbell. 4. Data. Data have been processed, published, or are a v a i l a b l e on m i c r o f i l m as d i s - cussed under Project 3.1. A l l IGY data have been supplied to the data centers. 5. Results. Some unexpected r e s u l t s were obtained r e l a t e d to the inhomogeneity of the earth c o n d u c t i v i t y . The records are under study a t the Geophysical I n s t i t u t e of Alaska, and a paper has been prepared by a Coast and Geodetic Survey s c i e n t i s t out- l i n i n g a method f o r f i n d i n g l i n e currents from the d i f f e r e n t i a l records. 6. Bibliography. Hurwitz, Louis, "Differential-Magnetograph Exploration of Line Currents." (Pro- cessed). U. S. Coast and Geodetic Survey, 1958, 16 pp. 135

GEOMAGNETISM Project 3.8 - Operation of Rapid-Run A u x i l i a r y Magnetographs 1. Objectives, This program of the Coast and Geodetic Survey provided f o r recording f l u c t u a t i o n s i n the earth's magnetic f i e l d too r a p i d t o be resolved by the time scale of the standard magnetographs inasmuch as much research by many workers has shovm t h a t a great deal of important information can be obtained from the higher frequency com- ponents of the magnetic f l u c t u a t i o n s , 2. Operations. Instrumentation was b u i l t by Ruska, based on s p e c i f i c a t i o n s of the Coast and Geodetic Survey. Resulting grams are much easier to read and i n t e r p r e t than previously a v a i l a b l e equipment was capable of producing. I n s t a l l a t i o n s were made a t Tucson, Honolulu, S i t k a , College, Point Barrow, Healy, Big Delta, Guam, Koror, L i t t l e America, Byrd and Wilkes. Fredericksburg had already been equipped w i t h a rapid-run magnetograph. 3. Personnel. The p r o j e c t was under the supervision of E. B. Roberts, J. H. Nelson and Joel B. Campbell. 4. Data, Data are a v a i l a b l e on m i c r o f i l m as discussed under Project 3.1. A l l IGY data have been supplied to the data centers. 5. Results, The rapid-run magnetograms are c o n t r i b u t i n g to numerous studies and i n - v e s t i g a t i o n p r o j e c t s , as evidenced by the requests f o r copies of the grams from World Data Center A, The rapid-run equipment has been i n continuous operation a t the per- manent observatories since the close of the IGY. Pro j e c t 3,9 - Single Component V i s i b l e Recording Magnetographs 1. Objectives, This p r o j e c t of the Coast and Geodetic Survey was established mainly to a s s i s t the ionospheric physics program t o provide immediately accessible informa- t i o n on magnetic a c t i v i t y , 2. Operations. This p r o j e c t consisted of designing and purchasing magnetic v a r i o - meters ( f o r responding to changes i n D e c l i n a t i o n or Horizontal I n t e n s i t y ) and pen- and-ink recorders f o r i n s t a l l a t i o n a t ionosphere s t a t i o n s . The r e s u l t i n g magnetograms were not expected to be of f i r s t - q u a l i t y p r e c i s i o n and are therefore not preserved i n the archives of the IGY World Data Centers. However, judging by the requests f o r the equipment, and comments on i t s usefulness, i t helped to f i l l a r e a l need a t the f o l - lowing l o c a t i o n s : Hanover, N, H.; Un i v e r s i t y Park, Pa.; Boulder, Colo.; Pullman, Wash.; Stanford, C a l i f , ; Sunspot, N, M.; Thule AFB, Greenland; L i t t l e America, Ant- a r c t i c a ; and Knob Lake, Canada. Some t r o u b l e was experienced a t a few of the i n s t a l l a t i o n s , due e n t i r e l y t o mal- f u n c t i o n i n g of the recorder u n i t — a moderate p r i c e d , commercially a v a i l a b l e balanc- ing potentiometer device. Where these recorders could be replaced by the users w i t h a b e t t e r q u a l i t y instrument, performance was q u i t e s a t i s f a c t o r y . 3. Personnel. The p r o j e c t was under the supervision of E. B, Roberts, J, H, Nelson and Joel B, Campbell, 4. Data, Inasmuch as these instruments were not c a l i b r a t e d and used only f o r a u x i - l i a r y i n f ormation f o r the purposes of other programs, the records were not processed and are retained by the s c i e n t i s t s a t the operating s t a t i o n s . 136

GEOMAGNETISM Project 3.10 - Sub-Audio-Frequency Geomagnetic Fluctuations 1. Obiectives. The objectives of the program, which was a j o i n t e f f o r t of the Geo- physics Research D i r e c t o r a t e (GRD), A i r Force Cambridge Research Center, and the Den- ver Research I n s t i t u t e (DRI), U n i v e r s i t y of Denver, were to obtain a d e s c r i p t i o n of the geomagnetic f l u c t u a t i o n s i n the 1 t o 50 cps, frequency band and t o determine, as f a r as possible, the sources of the f l u c t u a t i o n s . The small amount of data a v a i l a b l e before the I n t e r n a t i o n a l Geophysical Year in d i c a t e d t h a t both atmospheric and iono- spheric sources could c o n t r i b u t e to the s i g n a l w i t h the l a t t e r becoming more important a t the higher l a t i t u d e s . There was also some evidence t h a t i n the a u r o r a l zone the larg e s t f l u c t u a t i o n s tended to precede, by i n t e r v a l s of several hours, the larg e r mag- n e t i c disturbances as measured by the K in d i c e s . 2. Operations. For the f i e l d measurement s t a t i o n s , s p e c i a l equipment was constructed i n c l u d i n g detector c o i l s using mu-metal cores, l o w - l e v e l a m p l i f i e r s using high-gain input transformers, fm modulators, and switching systems t o provide f o r automatic data sampling. Low-speed (0.3 inch/second) magnetic tape t r a n s p o r t s , c a l i b r a t i o n o s c i l l a - t o r s , and power supplies were procured f o r the f i e l d s t a t i o n . Three mutually perpen- d i c u l a r components of the 1 t o 50 c/s f l u c t u a t i o n s were recorded on 1/4 inch magnetic tape during the f i f t e e n - m i n u t e i n t e r v a l from 02 to 17 minutes a f t e r each hour. For the c e n t r a l monitoring s t a t i o n a t DRI, a standard tape recorder (30 inches/second f o r playback), octave band-width f i l t e r s covering the 1 t o 50 c/s range, and pen-and-ink recorders were procured. F i e l d recording s t a t i o n s were located a t : Thule, Greenland (June 1958 - Dec. 1958) Fort Devens, Mass. (March 1958 - Dec. 1958) Mt. Evans, Colorado (May 1958 - Dec. 1958) College, Alaska (Sept. 1958 - Dec. 1958) Ramey AFB Since much of the equipment had to be developed e s p e c i a l l y f o r t h i s work, there was considerable delay i n g e t t i n g the s t a t i o n s i n t o operation. Accordingly, opera- tion s were continued w e l l beyond the formal IGY period ( i n f a c t , w e l l i n t o 1960) i n order to secure a representative sample of data. An a d d i t i o n a l s t a t i o n a t Huancayo, Peru, was also a c t i v a t e d a f t e r the close of the IGY t o extend the geographic coverage, 3. Personnel. The p r o j e c t was organized and c a r r i e d out under the d i r e c t i o n of Elwood Maple, GRD. Dr. A, R. Jordan, who supervised the p a r t i c i p a t i o n of DRI a t the beginning of the program, has since l e f t t h a t i n s t i t u t i o n , and Dr. A l v i n W. Jenkins i s now i n charge there. Other key personnel have been Don F. Smart (GRD) and Charles Sawyer (employed under contract w i t h the American Geographical Society) who operated the Thule s t a t i o n , and a t DRI, Charles A. P h i l l i p s , J r . 4. Data. The data are stored a t DRI on magnetic tapes. Since t h i s was a spe c i a l p r o j e c t w i t h no i n t e r n a t i o n a l counterparts, and because reduction of the data w i t h the o r i g i n a l equipment was an extremely slow process, no data have yet been submitted to the data centers. Since the close of the IGY, however, equipment has been devel- oped f o r automatic data redu c t i o n . Much of the 1958 IGY and the IGC-1959 recordings have now been reduced to tables of average s i g n a l l e v e l s . When r e l i a b i l i t y l i m i t s have been determined f o r the reduced data, they w i l l be made a v a i l a b l e f o r the use of other i n t e r e s t e d s c i e n t i s t s . When the tapes are played back, the s i g n a l f o r each of the three components (now i n the 100 to 5000 c/s range) i s fed t o s i x octave band-pass f i l t e r s , and the output 137

GEOMAGNETISM of each f i l t e r I s r e c t i f i e d and averaged by one of two a l t e r n a t i n g sets of RC c i r c u i t s having time constants of 100 seconds (equivalent t o 10^ seconds of recording t i m e ) . At the end of each 15 minute recording i n t e r v a l (9 seconds a t playback), the condenser voltages are read and punched i n t o paper tape, and the condensers are discharged before t h e i r next cycle. These values are then tabulated on a Flexowriter and may also be fed t o a d i g i t a l computer f o r s t a t i s t i c a l a n a l y s i s . The r e s u l t i n g tables thus contain eighteen values ( s i x frequency bands f o r each of the three components) f o r each hour of the day, 5. Results. A l l analysis to date has been based on average values of s i g n a l l e v e l . Most of the f l u c t u a t i o n s throughout the 1 t o 50 c/s range a r i s e from thunderstorm a c t i v i t y as may r e a d i l y be demonstrated by comparing the d i u r n a l and seasonal v a r i a - t i o n s of s i g n a l l e v e l w i t h the corresponding v a r i a t i o n s of the average worldwide thunderstorm d i s t r i b u t i o n and taking account of the d i r e c t i o n a l e f f e c t s of the detec- t o r c o i l s . Signal l e v e l s i n the 9.8 c/s band (6.8 t o 14.0 c/s) varied l e a s t as the average distance from the source v a r i e d , and a peak i n the frequency spectrum appeared i n t h i s band when the thunderstorm a c t i v i t y was comparatively d i s t a n t . This consistent feature of the data, when combined w i t h the narrow-band analysis of a small amount of data by Balser and Wagner who resolved the i n d i v i d u a l modes, confirms the resonant modes of the earth-ionospheric c a v i t y ( f i r s t described by Schumann) as a stable fea- ture of the propagation i n t h i s frequency range. The second t o f o u r t h modes would also c o n t r i b u t e t o the 19 c/s band. I n the highest frequency band used (center f r e - quency 34 c/s, 25 t o 46 c/s band) the i n d i v i d u a l higher order modes become less s i g n i - f i c a n t , and the estimated a t t e n u a t i o n of somewhat less than 1 db per 1000 km i s i n reasonable agreement w i t h the waveguide theory and observational data a t higher f r e - quencies. Below about 8 c/s (the fundamental resonant mode of the c a v i t y ) a t t e n t i a t i o n i n - creases w i t h decreasing frequency, but the wavelengths become so long t h a t the induc- t i o n f i e l d of the source i s o f t e n comparable t o or larger than the r a d i a t i o n f i e l d , and estimates of atte n u a t i o n become somewhat ambiguous. The observed increase of average s i g n a l s t r e n g t h w i t h decreasing frequency below 8 c/s f o r times of compara- t i v e l y close thunderstorm a c t i v i t y ( i , e , , average summer daytime c o n d i t i o n s ) does not agree w i t h current ideas of the power spectrum of the l i g h t n i n g discharge. Possible explanations might be the long c o n t i n u a t i o n of low c u r r e n t d e n s i t i e s i n the discharge channel as suggested by recent photographic observations or cloud-to-cloud or upward discharges from thunderstorm c e l l s whose spectra might d i f f e r from t h a t of the cloud- t o - e a r t h discharge. Fluctuations of ionospheric o r i g i n also appear i n the records but must be separated from the thunderstorm f l u c t u a t i o n s which u s u a l l y predominate, and t h e i r analysis has only begun. At middle l a t i t u d e s t a t i o n s there i s l i t t l e r e l a t i o n s h i p between average s i g n a l l e v e l s and the K indices of geomagnetic a c t i v i t y , but a weak c o r r e l a t i o n may be observed i n the 1 to 4 c/s range when the thunderstorm f l u c t u a t i o n s are q u i t e small ( i . e , , average w i n t e r n i g h t c o n d i t i o n s ) . P r i o r t o the s t a r t of t h i s program, single-component measurements a t Point Barrow, Alaska, had shown increased s i g n a l l e v e l s preceding by several hours many of the l a r - ger magnetic disturbances as measured by the l o c a l K in d i c e s . Examination of small amounts of data from College, Alaska, and Thule, Greenland, has revealed a few events of t h i s type a t College, but none a t Thnle. I f f u r t h e r analysis confirms these r e - s u l t s , such events could not be a t t r i b u t e d t o e f f e c t s of solar p a r t i c l e r a d i a t i o n i n the lower ionosphere, but the generation of hydromagnetic waves a t the outer f r i n g e of the geomagnetic f i e l d , as suggested by Parker, might be ap p l i c a b l e . 138

GEOMAGNETISM Enhanced signal levels attributed to meteor effects i n the lower ionosphere are sometimes observed, particularly tinder winter night conditions, i n the 1 to 2 and 2 to 4 c/s bands. The evidence for such effects i s strong but not yet conclusive, and further investigations are under way. Many special types of waveforms, probably attributable to ionospheric phenomena, have often been observed i n the course of f i e l d station operation, and i t i s hoped that equipment w i l l become available i n the future for a systematic survey of the characteristics of these phenomena i n the extensive tape recordings which have been accumulated. 6. Bibliography. a. Papers Presented at Meetings. E. Maple: "Sub-Audio-Frequency Geomagnetic Fluctuations." Fortieth Annual Meeting, American Geopl^rsical Union, Washington, D. C , May 4-7, 1959. E. Maple, A, W. Jenkins, C. A. P h i l l i p s : "Sub-Audio-Freqoency Geomagnetic Fluctuations at Denver, Colorado." For t y - F i r s t Annual Meeting, American Geophysical Union, Washington, D. C,, A p r i l 27-30, 1960. A. W. Jenkins, C. A. P h i l l i p s , E. Maple. "Observed Correlation Between Geomagnetic Fluctuations and Meteor Rates." For t y - F i r s t Annual Meeting, American Geophysical Union, Washington, D. C , A p r i l 27-30, 1960. E. Maple. "Sub-Audio-Frequency (1 to 50 cps) Geomagnetic Fluctuations." International Association of Geomagnetism and Aeronomy, X I I General Assembly of lUGG, Helsinki, Finland, July-August 1960. b. Published Papers: A. W. Jenkins, C. A. P h i l l i p s , and E. Maple: "Observed Magnetic Effects from Meteors." JGR. vol. 65, no. 5, May 1960, pp. 1617-1619. 139

GEOMAGNETISM Project 3.11 - Magnetic Observations a t J a r v i s , Palmyra and Fanning 1. Objectives. Temporary magnetic observatories were established under t h i s p r o j e c t , and operated f o r about one year during the IGY, by the Scripps I n s t i t u t i o n of Oceano- graphy, Uni v e r s i t y of C a l i f o r n i a , La J o l l a , C a l i f o r n i a , on J a r v i s , Palmyra and Fan- ning I s l a n d s , and f o r one month on Christmas I s l a n d , f o r the purpose of studying the anomalous behavior of the magnetic f i e l d i n the v i c i n i t y of the magnetic eqtiator. 2. Operations. The bulk of the instrumentation required f o r the p r o j e c t was procured, from other funds, by the Coast and Geodetic Survey. This included three three-compo- nent Askania Variographs, recording changes of D, H and Z, three contact clocks f o r providing time marks on the variograph records, three chronometers, and two theodo- lite-magnetometer-inductors f o r absolute determinations of D, H and I . The Coast Survey also provided f a c i l i t i e s f o r t r a i n i n g the observers. The Scripps I n s t i t u t i o n undertook r e s p o n s i b i l i t y f o r a l l other aspects of the p r o j e c t , f o r engaging personnel, f o r p r o v i d i n g s h e l t e r s and the necessary power supplies f o r the recording equipment, and f o r l o g i s t i c support of the operation, i n c l u d i n g communications. Because of the remoteness of the Line Islands and the i m p o s s i b i l i t y of maintaining day-to-day c o n t r o l of the operation from Scripps i t was decided t o appoint a F i e l d Party Chief who would be f u l l y responsible f o r a l l aspects of the f i e l d operation. Further, because of the inhospitable nature of J a r v i s , i t was decided t h a t a boat should be permanently a v a i l a b l e i n the area f o r supplies, r e l i e f of personnel and emergency use. These two requirements were met by cha r t e r i n g a s a i l i n g boat, w i t h a u x i l i a r y engine, capable of s a i l i n g between Hawaii and the Line Islands and w i t h a captain who was q u a l i f i e d t o act as F i e l d Party Chief. The l a t t e r was assisted by three t r a i n e d observers and by one f u l l - t i m e and several part-time a s s i s t a n t s . I t was i n i t i a l l y planned t o make measurements over a period of about 15 months. However, i t turned out t h a t J arvis and Fanning operated f o r a l i t t l e over 16 months, w i t h about 80% complete records, and Palmyra f o r 12 months, w i t h 50% complete records. Most of the gaps were due to instrumental t r o u b l e s , some of which required spare parts to be obtained from the mainland. The Jarvis s t a t i o n was closed down f o r three weeks during October 1958 because of the death of the observer. The Palmyra s t a t i o n was tran s f e r r e d to Christmas Island f o r the month of December 1958. Invaluable assistance was obtained from the B r i t i s h a u t h o r i t i e s , who l e f t i n t a c t on Jarvis the i n s t a l l a t i o n s provided f o r a s c i e n t i f i c party working i n the area p r i o r to the beginning of the p r o j e c t and who a i r l i f t e d both personnel and supplies between Hawaii and Christmas I s l a n d . The B r i t i s h company. Cable and Wireless, generously made av a i l a b l e t o the p r o j e c t the supply, workshop and s o c i a l f a c i l i t i e s of t h e i r cable s t a t i o n on Fanning I s l a n d . 3. Personnel. The p r o j e c t was under the general supervision of Dr. Ronald Mason of the Scripps I n s t i t u t i o n who v i s i t e d the Line Islands during the setting-up phase and towards the end of the operating period and who provided l i a i s o n between Scripps and the f i e l d p r o j e c t on s c i e n t i f i c matters. Dr. Martin Vitousek was the F i e l d Party Chief and skippered his own vessel, the FIESTA, f o r supply operations, 4. Data. Data from Jarvis have been processed and published as Coast and Geodetic Survey P u b l i c a t i o n HV-JI58. Data from Fanning w i l l be d e a l t w i t h s i m i l a r l y . A l l other data from the IGY period have been submitted to the data centers and are a v a i l - able on m i c r o f i l m as discussed under p r o j e c t 3.1. 5. Bibliography. R. G. Mason and M. J. Vitousek. "Some Geomagnetic Phenomena Associated w i t h Nuclear Explosions." Nature, v o l . 184, pp. B, A. 52-54, 1959. E x p l o i t a t i o n of the data i s the subject of an NSF grant t o the Scripps I n s t i t u - t i o n , Grant Y/22.12/312 - Line Islands Geomagnetic Data. 140

GEOMAGNETISM Projects 3.12, 3.15 and 3.17 Equipment f o r Magnetic Stations a t J a r v i s , Palmyra, Fanning, A r c t i c Ice Floe ( S t a t i o n A ) , and the South American 5-Station Network. 1. Objectives. I n the p r o j e c t s l i s t e d here the Coast and Geodetic Survey was i n - volved to the extent of supplying instrumentation; other agencies were responsible f o r the operating programs. 2. Operations. Recording equipment f o r each p r o j e c t consisted of Askania Vario- graphs (semi-portable 3-component magnetographs) of s u i t a b l e s e n s i t i v i t i e s , together w i t h mechanisms f o r supplying adequate time c o n t r o l and time marks on the records. Magnetometers and earth-induetors were furnished f o r absolute c o n t r o l of base-line values a t the Jarvis-Palmyra-Fanning s t a t i o n s . A t r a n s i t magnetometer f o r observa- t i o n s of De c l i n a t i o n and H o r i z o n t a l I n t e n s i t y was shipped to the Ice Floe S t a t i o n A, but both recording and c a l i b r a t i n g instruments a t t h i s s t a t i o n were l o s t when the s t a t i o n was abandoned because of the sudden break-up of the s t a t i o n s i t e i n November 1958. 141

GEOMAGNETISM Project 3.16 - Equatorial E l e c t r o j e t i n Peru 1. Objectives. The f i r s t o b j e c t i v e of t h i s i n v e s t i g a t i o n under the cognizance of the Department of T e r r e s t r i a l Magnetism, Carnegie I n s t i t u t i o n of Washington, was to determine the l a t i t u d e v a r i a t i o n of the amplitude of the d i u r n a l v a r i a t i o n of the three magnetic components (D, H, and Z), These r e s u l t s , important i n themselves, were used t o choose locations f o r the operation of four temporary IGY magnetic ob- servatories from which data would be used to i n v e s t i g a t e e l e c t r o j e t e f f e c t s i n other types of temporal changes i n a d d i t i o n t o the normal d i u r n a l v a r i a t i o n s , 2. Operations. Four Askania Variographs were made a v a i l a b l e f o r the p r o j e c t by the U. S. Coast and Geodetic Survey. Two were used i n a survey i n which the d i u r n a l var- i a t i o n i n D, H, and Z was recorded f o r two or three days a t each of 15 s t a t i o n s bet- ween the geographic equator and l a t i t u d e 22°S. This survey i n a d d i t i o n to providing a basis f o r s e l e c t i n g the l a t i t u d e s of the s i t e s f o r continuous operation of the four variographs during the IGY and IGC period also provided invaluable data f o r determin- ing the e x t e r n a l current system f o r the e l e c t r o j e t . 3. Personnel. The l a t i t u d e survey was c a r r i e d out j o i n t l y by Scott E, Forbush of the Department of T e r r e s t r i a l Magnetism, Carnegie I n s t i t u t i o n of Washington, and Mateo Casaverde of the I n s t i t u t e Geofisico de Huancayo. The operation of the four variographs a t the selected IGY (and IGC) s i t e s was c a r r i e d out under the general supervision of Mateo Casaverde who also supervised the sca l i n g and conversion of hourly values o f the components, 4. Results, During the IGY and IGC e s s e n t i a l l y continuous complete data were ob- tain e d , simultaneously a t the four IGY observatories and a t Huancayo f o r 20 magneti- c a l l y q u i e t days and f o r 10 magnetically disturbed days i n each of three seasons, Magnetograms w i t h H, D, and Z traces were obtained on the west coast of South America between the geographic equator and l a t i t u d e 22°S a t f i f t e e n temporary survey s t a t i o n s , a t four I n t e r n a t i o n a l Geophysical Year observatories, and a t Huancayo, Analysis of these shows t h a t the primary Sg e l e c t r o j e t near midday i s a band, about 660 km wide, of eastward current a t about 100 km height centered over the dip equa- t o r , near which i t accounts f o r about h a l f the t o t a l range of Sq i n H, The induced f i e l d of the Sq j e t i s compatible w i t h t h a t of i t s negative Image a t 600 km depth and consistent w i t h r e s u l t s from an analysis of a bay disturbance i n the a u r o r a l zone. No j e t e f f e c t s are found a t n i g h t , and there i s no evidence f o r seasonal changes i n the l o c a t i o n of the j e t . The center of the j e t foll o w s the secular change i n the geographic l a t i t u d e of the dip equator. There i s no evidence f o r j e t e f f e c t s i n Dsx, Jet e f f e c t s are found near midday f o r sudden commencements, f o r s o l a r - f l a r e e f f e c t s ( c r o c h e t s ) , and f o r sudden changes, probably associated w i t h Sp disturbances. For the average of s o l a r - f l a r e e f f e c t s near midday, the r a t i o of the j e t e f f e c t near the d i p equator t o the "normal" f o r the j e t e f f e c t i s about twice the corresponding r a t i o f o r the aver- age Sq j e t . For sudden commencements a t n i g h t , the v e r t i c a l f i e l d changes sign a t geographic l a t i t u d e 8°S, which corresponds to the l o c a t i o n of Simpson's cosmic-ray equator a t the same longitude; the change i n sign of A Z f o r these sudden commence- ments occurs w i t h i n a narrow range of l a t i t u d e , i n d i c a t i n g t h a t the current system responsible f o r sudden commencements probably flows i n the upper atmosphere, 5. Bibliography, Scott E, Forbush and Mateo Casaverde: "The Equatorial E l e c t r o j e t i n Peru," CIW P u b l i c a t i o n No. 620, (Includes complete tabulations of hourly values f o r the survey data and f o r the days mentioned i n No, 4 above,) 142