The Sun to the Earth – and Beyond Panel Reports (2003) / Chapter Skim
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3 Report of the Panel on Atmospheric-Ionosphere-Magnetosphere Interactions
3 Report of the Panel on Atmospheric-Ionosphere-Magnetosphere Interactions
Pages 125-182
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From page 125... ...
SSUMMARY 1 27 3.1 INTRODUCTION 132 3.2 SCIENCE THEMES AN D OPPORTU N ITIES FOR THE COMI NG DECADE 1 38 Earth as a Particle Accelerator 138 Earth's Electric Field 142 Volati le Weather in the Upper Atmosphere 1 46 Micro- and Mesoscale Control of Global Processes 1 53 Dynamics of Geomagnetic Storms, Substorms, and Other Space Weather Disturbances Sol ar Vari abi I ity and C I i mate 1 59 Magnetospheric, ionospheric, and Atmospheric Processes in Other Planetary Systems 161 3.3 SOCIETAL IMPACT OF SPACE WEATHER 164 Communications 1 65 Navigation 1 67 Electric Power Issues 168 Astronaut, Ai rl i ne, and Satel I ite Hazards 1 69 Satel I ite Drag and Col I ision Avoidance 1 69 3.4 EXISTI N G PROG RAMS AN D N EW I N ITIATIVES 3.5 TECH NOLOGIES FOR THE FUTU RE 1 71 Data Assimi ration 1 71 S pacec raft an d I n stru ment Tech n o l ogy 3.6 RECOMMEN DATIONS 173 Major NSF Initiative 1 74 NASA Orbital Programs 176 NASA Suborbital Program 178 Societal I mpact Program 1 78 Maxi mizi ng Scientific Return 1 80 BIBLIOGRAPHY 1 82 1 72 125
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From page 127... ...
STRATEGY AND REQUIREMENTS The next decade may revolutionize our understanding of the dynamical behavior of the A-l-M system in response to driving from both the solar wind and the lower atmosphere. A carefully orchestrated collaboration between agencies with interest in space weather and space science research is required, since no one agency has the resources to provide the global view.
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From page 128... ...
Data assimilation technologies are crucial for integrating new observations into research and operational models of the space environment. The problems associated with the transition of research models and data sets to operations must be specifically addressed in the planning and implementation of research programs aimed at i mprovi ng space weather forecast)
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From page 129... ...
Highest priority would be given to a facility at the same geographic latitude as one of the existing radar sites. NASA Orbital Programs The Explorer Program has since the beginning of the space age provided opportunities for studying the geospace environment just as the Discovery Program now provides opportunities in planetary science.
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From page 130... ...
Many phenomena have been discovered using rockets, rockoons, and teal loons, and many outstand i ng problems brought to closure, particularly when space-based facilities are THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS teamed with ground-based facilities. These phenomena include the auroral acceleration mechanism, plasma bubbles at the magnetic equator, the charged nature of polar mesospheric clouds, and monoenergetic auroral beams.
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From page 131... ...
The societal impacts of space weather are broad commu n Cations, navigation, human radiation hazards, power distribution, and satellite operations are all affected. Space weather is of international concern, and other nations are pursuing parallel activities, which could be leveraged through collaboration.
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From page 132... ...
During these events, Earth is engulfed in intense high-frequency radiation, vast clouds of energetic particles, and fast plasma flows with entrained solar magnetic fields. Even though only a small fraction (generally <10 percent)
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From page 133... ...
Small Instrument Distributed GroundBased Network Recommended 10-Year Funding (million $) 800 500 350 Subtotal 1,650 92 300 50 100 Subtotal 542 Small Suborbital program NSF Supporting Research and Technology National Space Weather Program 50 NSF SHINE, CEDAR, GEM, C-A-I-M (new)
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From page 134... ...
close-up of radiation belts (trapped particles) , including inner and outer zone populations and trapped anomalous cosmic rays (interstellar matter)
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From page 135... ...
Substorms may actually sever the outer plasma sheet from the magnetotail, producing a major loss of plasma and energy. Dipolarization of the magnetic field during substorms, which reduces the stretching of magnetotail field lines, generates intense electric fields, which accelerate the storm-enhanced plasma sheet.
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From page 136... ...
Lightning activity in tropospheric thunderstorms imposes huge transient electric fields on the middle atmosphere, leading to intense heating and ionization, manifested by transient luminous displays known as sprites and elves. These same electric fields can drive avalanche acceleration of relativistic electron beams, which produce gamma-ray emissions during their upward traverse and may escape into the radiation belts.
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From page 137... ...
The maturity of the A-l-M discipline leads to a close connection between A-l-M science and applications for the benefit of society. The application of space physics and aeronomy to societal needs is now referred to as space weather.
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From page 138... ...
During large geomagnetic storms, rapidly time-varying electric fields and currents, often co-located with the aurora, intensify and expand to lower latitudes, sometimes producing power outages that affect transmission I i nes th rough G ICs. With i mproved forecast)
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From page 139... ...
Where an aurora occurs, a variety of associated physical phenomena occur along the magnetic field line that threads the ionospheric end where the light emission occurs. Just as electrons are accelerated downward, ions are also accelerated upward to the same energies.
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From page 140... ...
On the theoretical side, it is time to develop models that can handle an entire auroral field line; the effects of precipitating electrons, protons, and heavier ions; and the physics of the cold, dense ionospheric plasma, using nonideal magnetobydrodynamic and two-fluid simulations evolving to include two- and three-dimensional particle effects. THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS Ring Current The ring current, consisting of ions ranging in energy from tens to hundreds of keV, embodies sufficient plasma pressure to reduce the magnetic field locally and measurably at equatorial locations on Earth's surface, especially during geomagnetic storm periods of enhanced convection, u Itimately driven by the solar wind.
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From page 141... ...
One sees a strong correlation between flux enhancements and this measure of geomagnetic storms, strongest when it is most negative, since the ring current opposes and reduces the magnetic field due to Earth's dipole. Radiation belt electron fluxes build up at lower L values during stronger geomagnetic storms, posing a greater threat to constellations of spacecraft such as the GPS and to the International Space Station during those times.
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From page 142... ...
These interplanetary electric fields map down the magnetic field lines, particularly when the interplanetary magnetic field has a southward component, and even reach the stratosphere. From below, the atmosphere acts as a hydrodynamic generator, creati ng electric fields rangi ng from planetary scales and tidal periods down to turbulent eddies and polarized structures smeller then a kilometer.
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From page 143... ...
Dependencies on interplanetary magnetic field orientation, solar wind dynamics, and magnetospheric activity usually produce a situation that is much more complex. Although the study of electric fields in the polar region has seen many successes in understanding the basic configurations of the polar cap potential structure, the understanding in terms of fundamental theoretical models remains sketchy at best.
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From page 144... ...
Intense electric fields are produced that map up field lines to the inner magnetosphere. These strong and structured electric fields alter the drift paths of the ring-current ions that originally created them and produce structuring of the plasmasphere.
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From page 145... ...
If the convection is strong and long lasting, such as during geomagnetic storms, neutral winds can be accelerated in the direction of convecting ions owing to collisions between the ions and neutrals. Mapping of electric fields along field lines is violated when parallel electric fields develop in the auroral acceleration region.
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From page 146... ...
If they do, as recent rocket data suggest, they would have a considerable effect on ionospheric physics, space weather, and the magnetosphere. The magnetic field lines act as such good conductors that the electric field maps throughout the magnetosphere.
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I n the coming decade, we will begin the next step, moving into the predictive era for this important space weather problem. Crucial to success is fully understanding the equatorial electric field since it will be the single most important parameter in any prediction scheme.
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Ionospheric convection due to electric fields perpendicular to the background magnetic field is well understood in principle, but its application in ionospheric models fails to match reality because the sources of
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From page 149... ...
Candidate locations include deep in the polar cap, which has never been studied using the ISR technique, and the off-equatorial zone to study effects of equatorial ionospheric upwelling and downflow along magnetic field lines to adjacent latitudes, which can severely affect communications. One Atmosphere: Upward Coupling of Energy One of the major unresolved issues in a quantitative description of the A-l-M system is the extent of upward coupling of energy and momentum from the lower atmosphere.
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From page 150... ...
Recent studies also show that between 1 5 and 25 percent of observed ionospheric electron density variations cannot be ascribed to space weather or geomagnetic activity but are probably attributable to waves of tropospheric origin. The wave drivers can only be resolved with additional satellite measurements that are analyzed in concert with observations from groundbased networks.
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From page 151... ...
At low latitudes, with the nearhorizontal magnetic field, the neutral wind-driven electric fields dominate the plasma structure, giving rise to the equatorial ionization crests on both sides of the magnetic equator and anomalous wind and tempertaure features. The redistribution of plasma sets up conditions conducive to the generation of equatorial convective storms.
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From page 152... ...
This coupling mechanism between solar activity, solar wind structures, the energetic particle populations within the
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From page 153... ...
Understanding the scale sizes of the parallel electric fields that accelerate auroral particles is an important and active area of research. Models based on the reflection of electrons out of a converging magnetic field pro
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At Earth's magnetopause, reconnection results in the formation of open magnetic field lines, leading to exchange of mass along open flux tubes and an efficient transfer of solar wind momentum and energy by magnetic stresses. Nightside reconnection is considered to be critical for releasing magnetic energy stored in the tail.
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From page 155... ...
U nderstandi ng of the reconnection process in the magnetosphere will be a significant step toward the understanding of related phenomena occurring in astrophysics, solar physics, and laboratory plasma physics. DYNAMICS OF GEOMAGNETIC STORMS, SUBSTORMS, AND OTHER SPACE WEATHER DISTURBANCES There are a number of different modes of geomagnetic activity, including magnetic storms and substorms.
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From page 156... ...
Large solar wind dawn-to-dusk electric fields associated with these southward interplanetary magnetic fields are mapped down along magnetic field lines across Earth's polar cap and magnetotail. These electric fields are associated with a strong convection that draws plasma from the magnetotail deep into the inner magnetosphere.
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From page 157... ...
The large electric fields are located predominantly at the poleward edge of the high-latitude plasma sheet observed by Polar and appear to be correlated with substorm activity. The electric and magnetic fields have also recently been
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From page 158... ...
Both ENA images and ringcurrent models suggest that the enhanced convection electric field during storm activity moves ion injections deep into the inner magnetosphere, where they are strongly energized to form the storm-time ring current. THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS In the absence of strong convection, during isolated substorms, these injections have essentially no impact on ring-current formation but act to enhance the crosstail current at large radial distances.
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From page 159... ...
and ionization of the neutral atmosphere (at subauroraland midlatitudes) and to alterations in the minor species chemistry is not yet understood.
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From page 160... ...
Solar Irradiance Variability and Climate Since the Sun is the ultimate driver of our climate system, it is reasonable to suspect that there might be a link between solar variability and the changes in climate that are known to have taken place in the distant and recent past and are probably continuing to take place at the present time. Despite many claims of correlations between solar-activity indicators and climate variables, THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS however, the existence of such a link has been hard to prove.
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From page 161... ...
Si nce clouds have a major i nfl uence on cl imate and the terrestrial radiation budget, they could provide a powerful means of amplifying the effects of solar variability, if a connection to solar variability can be shown to exist. The flux of galactic cosmic rays striking Earth varies in intensity over 11-year intervals, in antiphase with the solar magnetic activity cycle, as a result of interactions between the cosmic ray particles and the interplanetary magnetic fields.
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From page 162... ...
By contrast, the external plasma environment (e.g., solar THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS wind) interacts rather directly with the upper atmospheres and ionospheres of bodies that have small intrinsic magnetic fields, such as Venus, Mars, Titan, and comets.
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From page 163... ...
The proposed Messenger mission is a start in this direction. Electrodynamical Coupling Processes at Weakly Magnetized Planets and Bodies The solar wind is able to interact directly with the atmosphere and ionosphere of a planet or object pos1 63 sessing only a weak intrinsic magnetic field.
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From page 164... ...
Whi le relevant activities have been pursued by NOAA and DOD for many years, the science community has only recently become more closely connected with this pursuit, since the inception of the National Space Weather Program i n 1 995 and NASA's Livi ng With a Star program. The NSWP is a multiagency endeavor to understand the physical processes, from the Sun to Earth, that result in space weather and to transition advances in science into operations in order to assist users affected by the space environment.
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From page 165... ...
Likewise, Japan has a solar cycle's worth of energetic particle data from the polar-orbiting Akebono satellite to contribute to radiation belt studies, and comparisons between YoLkoh x-ray images of the Sun during the last solar cycle and images that will be obtained from the new x-ray imager to be flown on the GOES spacecraft will provide an important cycle-to-cycle and long-term baseline on x-ray input to the atmosphere. A brief review of the principal space weather effects follows.
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From page 166... ...
and solar proton events (the classic polar cap absorption) , both of which change the lowest usable frequency.
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From page 167... ...
Communications systems at higher frequencies that are less susceptible to space weather effects are also used by airlines, but these additional capabilities are not available at all locations, particularly in the northern polar region. Near the poles, the ionosphere becomes strongly modified during large solar proton events.
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From page 168... ...
More recently, the smaller but still significant geomagnetic storm on July 15 and 16, 2000, caused voltage variations and tripping of protective devices at many locations in the United States. During large geomagnetic storms, rapidly time-varying electric fields and currents that are often co-located THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS with the auroral oval intensify and expand to lower latitudes and broaden in area to expose large portions of Earth's surface to this destructive source of energy.
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From page 169... ...
satellites; the National SpaceWeather Program; the NSFinitiated SHINE, GEM, and CEDAR programs and their international counterparts; NOAA's space weather programs; the International Space Environment Services program; and numerous DOD activities. These programs have supported satellite and ground-based monitoring instruments and the related data analysis and theory and modeling efforts.
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From page 170... ...
is needed to place the system's microscale drivers THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS in the context of the solar wind energy input that they mediate and the global system response that they engender. Such a cluster in equatorial orbit would give us a global knowledge of the zonal electric field at the magnetic equator the single most important parameter needed for predicting space weather disturbances there.
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From page 171... ...
Of particular importance is the development of adaptive grid technologies for models that address the large range of spatial and temporal scales characteristic of the global system structure and response. However, the A-l-M system is not simply multiscale, but it also requires inclusion of additional physical processes in boundary layers, transitioning between weak and strong magnetic field regions and coupling ionized and neutral populations across substantial gradients in density, flow velocity, energy, pitch angle, and species for example, along magnetic field lines.
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From page 172... ...
There are numerous data assimilation methods avai fable in meteorology and oceanography that can be applied to the space environment. SPACECRAFT AND INSTRUMENT TECHNOLOGY There are several areas of technological development that are needed to implement A-l-M objectives on future missions efficiently.
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From page 173... ...
For example, how does the magnetosphere limit solar wind power input, manifest in saturation of the polar cap potential ? How do the neutral atmosphere and the ionosphere respond to sudden and long-term changes on the Sun?
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From page 174... ...
Initial location at Poker Flat, Alaska, will allow coordination of radar with in situ rocket measurements of auroral processes. Subsequent transfer to the deep polar cap will enable studies of polar cap convection and the mapping of processes deeper in the geomagnetic tail.
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From page 175... ...
But despite four decades of magnetospheric research, much about the operation of these fundamental processes remains unknown or poorly understood.This state of affairs is in large part attributable to the limitations imposed on previous studies by their dependence upon single-spacecraft measurements,which are not adequate to reveal the underlying physics of highly dynamic, highly structured space plasma processes. To overcome these limitations, MMS will employ four co-orbiting spacecraft, identically instrumented to measure electric and magnetic fields, plasmas, and energetic particles.The initial parameters of the individual spacecraft orbits will be designed so that the spacecraft will form a tetrahedron near apogee.Thus configured, the MMS ~cluster"will be able to measure three-dimensional fields and particle distributions and their temporal variations and three-dimensional spatial gradients with high resolution while dwelling in the key magnetospheric boundary regions,from the subsolar magnetopause to the high-latitude magnetopause, and from the near tail to the distant tail.
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From page 176... ...
The full AMISR will have three faces, each of which is a phased-array ISR capable of pulse-to-pulse beam swinging.The system will provide measurements of electric fields, ion and electron temperatures, electron density, ion composition, and neutral winds in the meridian plane.Three faces will allow a very wide area to be studied from a single location. Alternatively, the faces can be deployed separately since each is in its own right a very powerful system.
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From page 177... ...
Moreover,the stresses that apparently continue to occur in the sounding rocket and balloon programs of NASA suggest that the suborbital program also is very limited in the access to space it gives for young scientists and engineers and as a hands-on training ground for them. See A Space Physics Paradox for further discussion.3 It would seem that NASA has identified larger-spacecraft missions as its primary focus of attention and funding.This means that very small, Pl-class spacecraft missions are not a high priority for it.
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From page 178... ...
To further ensure the vibrancy of the Suborbital Program, an independent scientific and technical panel should be formed to study how it might be changed to better serve the community and the country. SOCIETAL IMPACT PROGRAM The practical impact on society of variations in the A-l-M system falls into two broad categories: the wellestablished effects of space weather variations on technology and the less clear yet tantalizing influence of solar variability on climate.
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From page 179... ...
The National Space Weather Program should be strengthened and used as a template for interagency cooperation. International participation in such large scope programs as LWS and NSWP is essential.
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From page 180... ...
Available on I i ne at |
From page 181... ...
need to be applied to other planets and bodies, so that the study of solar-planetary relations becomes the natural extension of the terrestrial space weather effort.Achieving this goal will require several elements, including NASA planetary missions dedicated to A-l-M goals (or including significant A-l-M capabilities) ,a Discovery program in which A-l-M missions are included,and a grants program within NSF that is dedicated to comparative atmospheres, ionospheres, and magnetospheres (C-A-I-M)
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From page 182... ...
NSF.1997. National Space Weather Program: The Implementation P/an, FCM-P31 -1997.
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