Severe Space Weather Events Understanding Societal and Economic Impacts: A Workshop Report (2008) / Chapter Skim
Currently Skimming:
1 Introduction
1 Introduction
Pages 6-15
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 6... ...
Defining and quantifying these impacts presents a number of questions and challenges with respect to the gathering of the necessary data, the methodology for assessing the risks of severe space weather disturbances as low-frequency/high-consequence events, the perception of risk on the part of policy makers and stakeholders, and the development of appropriate risk management strategies. As a first step toward charting the dimensions of the problem of determining the socioeconomic impacts of extreme space weather events and addressing the questions of space weather risk assessment and management, a public workshop was held on May 22-23, 2008, in Washington, D.C., under the auspices of the National Research Council's (NRC's)
|
From page 7... ...
"The electricity which attended this beautiful phenomenon took possession of the magnetic wires throughout the country," the Philadelphia Evening Bulletin reported, "and there were numerous side displays in the telegraph offices where fantastical and unreadable messages came through the instruments, and where the atmospheric fireworks assumed shape and substance in brilliant sparks." 6 In several locations, operators disconnected their systems from the batteries and sent messages using only the current induced by the aurora. 7 The auroras were the visible manifestation of two intense magnetic storms that occurred near the peak of the sunspot cycle.
|
From page 8... ...
. Low-latitude red auroras, such as those widely reported to have been observed during the Carrington event, are a characteristic feature of major geomagnetic storms.
|
From page 9... ...
But it would not be until the 1930s that the significance of their observations was appreciated, and a full picture of the phenomena that constitute what we now call "space weather" would not emerge until well into the space age.15 A major turning point in our understanding of space weather came with the discovery of coronal mass ejections (CMEs) in the 1970s and with the recognition that these, rather than eruptive flares, are the cause of non-recurrent geomagnetic storms.16 Large-scale eruptions of plasma and magnetic fields from the Sun's corona, CMEs contain as much as 1016 grams or more of coronal material and travel at speeds as high as 3000 kilometers/second, with a kinetic energy of up to 1032 ergs.17 Eruptive flares and CMEs occur most often around solar maximum and result from the release of energy stored in the Sun's magnetic field.
|
From page 10... ...
31 Without upstream solar wind measurements such as are provided today by the Advanced Composition Explorer, researchers can only speculate about the structure of the CME and the magnitude and precise orientation of the associated magnetic fields.32 What can be inferred with certainty from the intensity and duration of the September storm, however, is that very strong magnetic fields were associated with the CME and that their orientation was opposite that of Earth's. This allowed the two fields to merge and enormous amounts of energy to be transferred into the magnetosphere, producing the magnetospheric and ionospheric phenomena characteristic of a major magnetic storm: (1)
|
From page 11... ...
The occurrence of low-latitude auroras and the dramatic auroral displays witnessed at higher latitudes indicate that this was a severe storm as well, although recently analyzed data from Russian magnetic observatories show that it was less intense and of shorter duration than the September 2 storm.35 No solar eruptions were reported in association with the August event, and so the transit time or shock/CME speed cannot be determined. It is not known whether the CME was SEP-effective as well as geoeffective.36 However, it is not unreasonable to speculate that a less intense SEP event was associated with the August 28/29 storm.37 Space Weather Effects and Socioeconomic Impacts The August-September auroral and magnetic storms of 1859 were recognized by contemporaries as extraordinary events, and they still rank at or near the top of the lists of particularly severe geomagnetic storms.
|
From page 12... ...
. Moreover, intense SEP events present a significant radiation hazard for astronauts on the International Space Station during the high-latitude segment of its orbit as well as for future human explorers of the Moon and Mars who will be unprotected by Earth's magnetic field.42 In addition to such direct effects as spacecraft anomalies or power grid outages, a complete picture of the impact of severe space weather events on contemporary society, with its complex weave of dependencies and interdependencies, must include the collateral effects of space-weather-driven technology failures.
|
From page 13... ...
149. This is one of a collection of papers published in a special issue of Advances in Space Research dedicated to the August-September 1859 geomagnetic storms.
|
From page 14... ...
index is the standard measure of magnetic storm intensity. It is derived from measurements made at four low-latitude magnetic observatories of the depression in the magnitude of the horizontal component of the geomagnetic field.
|
From page 15... ...
rank the Carrington event against other severe storms in terms of sudden ionospheric disturbance, SEP fluence, CME transit time, storm intensity, and equatorward extent of the aurora. They conclude, "While the 1859 event has close rivals or superiors in each of the above categories of space weather activity, it is the only documented event of the last ~150 years at or near the top of all the lists," p.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.