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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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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS SUMMARY Earth is the single most interesting object in the uni- verse to its inhabitants, the only place where we can be certain that a suitable environment for life exists. Fur- thermore, its complex systems are close enough to study in the sort of detail we will never obtain elsewhere. Earth and its sister planets are embedded in the outer atmosphere of the Sun. This outer atmosphere is con- tinually being explosively reconfigured. During these explosive events, Earth is engulfed in intense high-fre- quency radiation, vast clouds of energetic particles, and fast plasma flows with entrained solar magnetic fields. Even though only a small fraction (generally <10 per- cent) of this energy penetrates into geospace, the effects are dramatic. Space science programs to date have given us a detai led understanding of the average behavior of the component parts of geospace, in effect providing us with climatologies upon which to base educated guesses about the dynamic behavior of the global system. To go beyond this and understand the coupling processes and feedback that define the instantaneous response of the global system is much more difficult. The atmosphere- ionosphere-magnetosphere (A-l-M) system occupies an immense volume of space. At the same time, processes on scales from micro to macro impact the global system response. GOALS AND OBJECTIVES The overarching goals are as follows: 1. To understand how Earth's atmosphere couples to its ionosphere and its magnetosphere and to the at- mosphere of the Sun and 2. To attain a predictive capability for those pro- cesses in the A-l-M system that affect human ability to live on the surface of Earth as well as in space. Researchers currently have a tantalizing glimpse of the physical processes controlling the behavior of some of the individual elements in geospace. Some of the crosscutti ng science issues are these: The instantaneous global system response of the A-l-M system to the dynamic forcing of the solar atmo- sphere, The role of micro- and mesoscale processes in control I ing the global-scale A-l-M system, 1 27 The degree to which the dynamic coupling be- tween the geophysical regions controls and impacts the active state of the A-l-M system, The physical processes that may be responsible for the solar forcing of climate change, The origin of the multi-MeV electrons in the outer magnetosphere and the cause of the pronounced fluc- tuations in their intensity, and The balance between internal and external forc- ing in the generation of plasma turbulence at low lati- tudes. These critical science issues thread the artificial boundaries between the disciplines. The maturity of the A-l-M disciplines 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 soci- etal needs is now referred to as space weather. The space weather phenomena that most directly affect life and society include radiation exposure extending from space down to commercial airline altitudes, communi- cations and navigation errors and outages, changes in the upper atmosphere that affect satellite drag and or- bital decay, radiation effects on satellite electronics and solar panels, and power outages on the ground due to geomagnetical Iy induced currents (GlCs), to name a few. STRATEGY AND REQUIREMENTS The next decade may revolutionize our understand- ing 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 collabora- tion 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. Furthermore, new ground-based and space-based ob- serving programs are required that make use of innova- tive technologies to achieve a simultaneous global view, highly resolved in space and time. Clusters of satellites flying in close formation can resolve dynamical response and separate spatial from temporal variations. New data storage and handling technologies are necessary to man- age the shear volume of data generated, the multisatellite correlations, the mapping between in situ observations and images, searches across distributed databases, and other essenti al fu ncti ons that wi I I be necessary i n the next decade to achieve an understanding of the entire system. The systems view requires enhanced efforts to de- velop global theoretical models of the Sun-Earth system, including the simultaneous development of new soft-

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1 28 ware technologies for efficient use of paral lel computing environments and adaptive grid technologies to address the large range in spatial and temporal scales character- istic of the global system structure and response. How- ever, the A-l-M system is not simply multiscale, but it also requires inclusion of additional physical processes of ionized and neutral gases made up of individual par- ticles. Data assimilation technologies are crucial for in- tegrating new observations into research and operational models of the space environment. The problems associ- ated with the transition of research models and data sets to operations must be specifically addressed in the plan- ning and implementation of research programs aimed at i mprovi ng space weather forecast) ng and specification. The National Science Foundation's (NSF's) highly successful Solar, Heliospheric, and Interplanetary Envi- ronment (SHINE) program, its Coupling, Energetics, and Dynamics of Atmosphere Regions (CEDAR) program, and its Geosphere Envi ran ment Model i ng (G EM) pro- gram, and the recent coordination of these groups into Sun-to-Earth analysis campaigns, highlight the need to focus this broad range of expertise on issues involved in coupling between the Sun, solar wind, magnetosphere, and ionosphere/atmosphere regions. To this end, NSF recently funded the Science and Technology Center for I Integrated Space Weather Model i ng. NSF's i Information technology initiatives should be utilized as much as pos- sible to develop important collaboration technologies in support of such major community analysis efforts. The investigation of planetary A-l-M systems reveals details of value to understanding the terrestrial system. Future planetary missions should regularly be outfitted to carry out at least a baseline set of observations of the upper atmosphere, the ionosphere, and the magneto- sphere. In addition, theoretical studies linking our un- derstanding of the terrestrial environment with other planetary environments are an effective way of bringing extensive knowledge of plasma and atmospheric pro- cesses in the terrestrial environment to bear on the inter- pretation of planetary phenomena. While the National Oceanic and Atmospheric Ad- ministration (NOAA) and the Department of Defense (DOD) have pursued space environment forecasting for many years, their connection to the science community was facilitated by the inception of the National Space Weather Program (NSWP) in 1995 and NASA's new Liv- ing With a Star (LOOS) program. The NSWP is a multi- agency endeavor to understand the physical processes, from the Sun to Earth, that result in space weather and to transition scientific advances into operational applica- tions. NASA's new LWS program represents an impor- THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS tent opportunity to provide measurements and develop models that will clarify the relationship between sources of space weather and their impact. Enhancements and innovations in infrastructure, data management and assi mi I ation, i nstru mentation, computational models, software technologies, and methods for transitioning research to operations are es- sential to support the future exploration of geospace. RECOMMENDATIONS In the next decade, NASA should give highest prior- ity to multispacecraft missions such as Magnetospheric Mu Itiscale (MMS), Geospace Electrodynamics Constel- lation (GEC), Magnetospheric Constellation (MagCon), and Living With a Star's geospace missions, which take advantage of adjustable orbit capability and the advanc- ing technology of smal I spacecraft. Missions that involve large numbers of simply instrumented spacecraft are needed to develop a global view of the system and should be encouraged. NSF, for its part, should support extensive ground-based arrays of instrumentation to give a global, time-dependent view of this system. Ground- and space-based programs should be coordinated as, for example, is being done in the Thermosphere-lono- sphere-Mesosphere Energetics and Dynamics (TIMED)/ CEDAR program to take advantage of the complemen- tary nature of the two distinct viewpoints. NASA, NSF, DOD, and other agencies should encourage the devel- opment of theories and models that support the goal of understanding the A-l-M system from a dynamic point of view. Furthermore, these agencies should work to- ward the development of data analysis techniques, us- ing modern information technology, that assimilate multipoint data into a three-dimensional, dynamic pic- ture of this complex system. Funding for the NASA Sup- porting Research and Technology (SR&T) program should be doubled to raise the proposal success rate from 20 percent to the level found in other agencies. SolarTerrestrial Probe (STP) flight programs should have their own targeted postlaunch theory, modeling, and data analysis support. Major NSF Initiative Simultaneous, multicomponent, ground-based ob- servations of the A-l-M system are needed in order to specify the many interconnecting dynamic and thermo- dynamic variables. As our understanding of the com- plexity of the A-l-M system grows, so does the require-

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS ment to capture observations of its multiple facets. The proposed Advanced Modular Incoherent Scatter Radar (AMISR) will provide the opportunity for coordinated radar-optical studies of the aurora and coordinated in- vestigations of the lower thermosphere and mesosphere, a region not well accessed by spacecraft. 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 mapping of pro- cesses deeper in the geomagnetic tail. 1. The National Science Foundation should extend its major observatory component by proceeding as quickly as possible with Advanced Modular Incoherent Scatter Radar (AMISR) and by developing one or more lidar- centered major facilities. Further, the NSF should begin an aggressive program to field hundreds of small auto- mated instrument clusters to allow mapping the state of the global system. Ground-based sensors have played a pivotal role in our understanding of A-l-M science and must continue to do so in the coming decade and beyond. Anchored by a state-of-the-art phased-array scientific radar, the $60 million AMISR is a crucial element for A-l-M. A distributed array of instrument clusters would provide the high temporal and spatial resolution observations needed to drive the assimilative models, which the panel hopes will parallel the weather forecasting models we now have for the lower atmosphere. Much of the neces- sary infrastructure for such a project has already been demonstrated in the prototype Suominet, a nationwide network of simple Global Positioning System (GPS)/me- teorology stations linked by the Internet. The proposed program would add miniaturized instruments, such as all-sky imagers, Fabry-Perot interferometers, very-low- frequency (VLF) receivers, passive radars, magnetom- eters, and ionosondes in addition to powerful GPS-based systems in a flexible and expandable network coupled to fast real-time processing, display, and data distribu- tion capabilities. Instrument clusters would be sited at universities and high schools, providing a rich hands-on environment for students and training with instruments and analysis for the next generation of space scientists. Data and reduced products from the distributed network would be distributed freely and openly over the Internet. An overall cost of $100 million over the 1 0-year plan- ning period is indicated. Estimated costs range from $50,000 to $1 50,000 per station depend) ng on i nstru- ments to be depl oyed. Adeq u ate fu nd i ng wou I d be i n- 1 29 eluded for the development and implementation of data transfer, analysis, and distribution tools and facilities. Such a system would push the state of the art in informa- tion technology as well as instrument development and . . . . m~n~atur~zat~on. Extendi ng the present radar-centered upper atmo- spheric observatories to include one or more lidar-cen- tered facilities is crucial if we are to understand the boundary between the lower and upper atmosphere. Fortunately, a number of military and nonmilitary large- aperture telescopes may become avai fable for transition to lidar-based science in the next few years. Highest priority would be given to a facility at the same geo- graphic 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 geo- space environment just as the Discovery Program now provides opportunities in planetary science. The contin- ued opportu n ities for U n iversity-CI ass Explorer (U N EX), Smal I Explorer (SMEX), and Medium-Class Explorer (MIDEX) missions, practically defined in terms of their funding caps of $14 million, $90 million, and $180 million, respectively, allow the community the greatest creativity in developing new concepts and a faster re- sponse time to new developments in both science and technology. These missions also provide a crucial train- ing ground for graduate students, managers, and engi- neers. Imager for Magnetopause-to-Aurora Global Ex- ploration (IMAGE), launched in March 2000, is an example of a h igh Iy successfu I Ml DEX mission; it was preceded by the first two ongoing SMEX missions, Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) and Fast Auroral Snapshot Explorer (FAST), launched in 1992 and 1996, which have provided enor- mous scientific return for the investment. The Aeronomy of Ice in the Mesosphere (AIM) SMEX was recently se- lected for launch in 2006. The UNEX program, after the great success of the Student Nitric Oxide Explorer (SNOE), launched in February 1998, has effectively been cancelled. This least expensive component of the Ex- plorer program plays a role similar to that of the sound- ing rocket program, with higher risk accompanying lower cost and a great increase in the number of flight opportunities. An increase in funding to $20 million per mission with one launch per year would make this pro- gram viable with modest resources.

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1 30 2. The SMEX and MIDEX programs should be vigor- ously maintained and the U N EX program should quickly be revitalized. The STP line of missions defined in the NASA Sun- Earth Connection (SEC) Roadmap (strategic planning for 2000 to 2025) has the potential to form the backbone of A-l-M research in the next decade. The missions that are part of the current program include TIMED, launched in February 2002, Solar-B, the Solar Terrestrial Relations Observatory (STEREO), MMS, G EC, and MagCon. After TIMED, launched in February 2002, the next A-l-M/STP mission, MMS, is in the process of instrument selection for a 2009 launch. The STP cadence, with one A-l-M mission per decade (TIMED was significantly delayed), has fallen behind the NASA SEC Roadmap projections. 3. The panel heartily endorses the STP line of missions and strongly encourages an increase in the launch ca- dence, with GEC and MagCon proceeding in parallel. The A-l-M research community has very success- fully utilized the infrastructure developed within the In- ternational Solar-Terrestrial Physics (ISTP) program. The integration of the data from spacecraft and ground-based programs beyond those funded by the ISTP itself such as those of NOAA, LANE, and the DOD have contrib- uted substantially to our understanding of the global system. Comparisons between the Sun-Earth system and other Sun-planet or stellar-planet systems provide im- portant insights into the underlying physical and chemi- cal processes that govern A-l-M interactions. Improved understanding of A-l-M coupling phenomena such as planetary and terrestrial auroras would benefit from such an approach. 4. The Sun-Earth Connection program partnership with the NASA Solar System Exploration program should be revitalized. A dedicated planetary aeronomy mission should be pursued vigorously, and the Discovery Pro- gram should remain open to A-l-M-related missions. NASA Suborbital Program The NASA Suborbital program has produced out- standing science throughout its lifetime. Many phenom- ena 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. This program continues to generate cutting-edge science with new instruments and data rates that are more than an order of magnitude greater than typical satellite data rates. Both unique altitude ranges and very specific geophysical conditions are accessible only to sounding rockets and balloons, particularly in the cam- paign mode. Many current satellite experimenters were trained in the Suborbital program, and high-risk instru- ment development can occur only in such an environ- ment. To accomplish significant training, it is necessary that a graduate student remain in a project from start to finish and that some risk be acceptable; both are very difficult in satellite projects. The high scientific return, coupled with training of future generations of space- based experimenters, makes this program highly cost- effective. The sounding rocket budget has been level-funded for over a decade, and many principal investigators (Pls) are discouraged about the poor proposal success rate as well as the low number of launch opportunities. The sounding rocket program was commercialized in 2000; in this changeover, approximately 50 civil service posi- tions were lost and the cost of running the program increased. Approved campaigns were delayed by up to a year, and it is not yet clear whether the launch rate will ever return to precommercial ized levels. Effectively, commercialization has meant a significant decline in funding for the sounding rocket program. An additional concern is that, as currently structured i.e., with a fixed, 3-year cycle for all phases of a sounding rocket project funding is not easily extended to allow gradu- ate students to complete their thesis work, because it is generally thought that such work should fall under the SR&T program, already oversubscribed. The rocket pro- gram has a rich history of scientific and educational benefit and provides low-cost access to space for uni- versity and other researchers. Further erosion of this pro- gram will result in fewer and fewer young scientists with experience in building flight hardware and will ulti- mately adversely affect the much more expensive satel- lite programs. 5. The Suborbital program should be revitalized and its funding should be reinstated to an inflation-adjusted value matching the funding in the early 1980s. To fur- ther ensure the vibrancy of the Suborbital program, an independent scientific and technical panel should be

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS 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 well- established effects of space weather variations on tech- nology and the less clear yet tantalizing influence of solar variability on climate. The societal impacts of space weather are broad commu n Cations, navigation, human radiation hazards, power distribution, and sat- ellite operations are all affected. Space weather is of international concern, and other nations are pursuing parallel activities, which could be leveraged through collaboration. The role of solar variability in climate change remains an enigma, but it is now at least being recogn ized as i mportant to our understanding of the natural as opposed to anthropogenic sources of cli- mate variabi I ity. 6. The study of solar variability both of its short-term effects on the space radiation environment, communi- cations, navigation, and power distribution and of its effect on climate and the upper atmosphere should be intensified by both modeling and observation efforts. NASA's LivingWith a Star program should be imple- mented, with increased resources for the geospace com- ponent. Missions such as the National Polar-orbiting Operational Envi ran mental Satel I ite Systems (N POESS) and the Solar Radiation and Climate Experiment (SORCE) are needed to provide vital data to the science community for monitoring long-term solar irradiance. NPOESS should be developed to provide ionosphere and upper atmosphere observations to fill gaps in mea- surements needed to understand the A-l-M system. An L1 monitor should be a permanent facility that provides the solar wind measurements crucial to determining the response of the A-l-M system to its external driver, and the NSWP should be strengthened and used as a tem- plate for interagency cooperation. International partici- pation in such large-scope programs as LWS and NSWP is essential. 7. The NOAA, DOE/LAN L, and DOD operational spacecraft programs should be sustained, and DOD launch opportunities should be utilized for specialized missions such as geostationary airglow imagers, auroral oval imagers, and neutral/ionized medium sensors. 1 31 NASA's new Living With a Star program can, over the next decade, provide substantial new resources to address these goals. It is crucial that there be overlap between the geospace and solar mission components of LWS for the system to be studied synergistically, that resources be adequate for the geospace component, and that theory, modeling, and a comprehensive data sys- tem, which will replace the ISTP infrastructure, be de- fined at the outset, as called for in the Science Architec- tu re Team (SAT) report fi nd i ngs. NSWP, a mu Itiagency endeavor establ ished in 1 995, addresses the potential Iy great societal impact of physical processes from the Sun to Earth that affect the near-Earth environment in ways as diverse as terrestrial weather. The program specifi- cally addresses the need to transition scientific research into operations and to assist users affected by the space environment. Such multiagency cooperation is essential for progress in predicting the response of the near-Earth space environment to short-term solar variability. The interagency cooperation established in the NSWP is outstanding and is a model for extracting the maximum benefit from scientific and technical pro- grams. It has also been effective at bringing together different scientific disciplines and the scientific and op- erations communities. Interagency cooperation has worked well in the AFOSR/NSF Maui Mesosphere and Lower Thermosphere Program, and it has been key to the success of the NOAA GOES and POES programs of meteorological satellites with space environment moni- toring capabilities. International multiagency coopera- tion has been very successful for the ISTP program, which involves U.S., European, Japanese, and Russian space agencies. Global studies require such interna- tional cooperation. The panel recognizes that much more science can be extracted by careful coordination of ground- and space-based programs. Maximizing Scientific Return Funding for NASA's Supporting Research and Tech- nology program, including guest investigator studies and focused theory, modeling, and data assimilation efforts, is essential for maximizing the scientific return from large i nvestme nts i n s pacec raft h ardware. Supporting Research and Technology Wh i le spacecraft hardware projects are con- centrated at relatively few institutions, the NASA SR&T program is the primary vehicle by which independent investigations can be undertaken by the broader com-

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1 32 munity. Likewise, NSF helps individual investigators to carry out targeted research through its Division of Atmo- spheric Sciences (ATM) base programs SHINE, CEDAR, and GEM. Such individual Pl-driven initiatives are the most inclusive, with data analysis as well as theoretical efforts and laboratory studies, and often lead to the high- est science return per dollar spent. The funding for such program elements falls far short of the scientific oppor- tunities, with the current success rate for submitted NASA SR&T proposals being 10 to 20 percent. Further- more, limited available SR&T funds have been used for guest investigator participation in underfunded STP-class flight programs. Without adequate MO&DA funding for NASA orbital and suborbital programs, the SR&T budget intended for targeted research on focused scientific ques- tions has been utilized to support broader data analysis objectives. 8. The funding for the SR&T program should be in- creased, and STP-class flight programs should have their own targeted postlaunch data analysis support. 9. A new small grants program should be established within NSF that is dedicated to comparative atmo- spheres, ionospheres, and magnetospheres (C-A-I-M). A new C-A-I-M grants program at NSF would allow the techniques (modeling, ground-, and space-based observations, and in situ measurements) that have so successfully been applied to A-l-M processes at Earth to be used to understand A-l-M processes at other planets. Such a comparative approach would improve our un- derstanding of these processes throughout the solar sys- tem, including at Earth. Currently, a modest $2 million planetary science program at NSF covers all of solar system science (except for sol ar and terrestrial stud ies), with only a small fraction going to planetary A-l-M re- search. Theory, Modeling, and Data Assimilation Theory and modeling provide the framework for in- terpreti ng, understand) ng, and visual izi ng diverse mea- surements at disparate locations in the A-l-M system. There is now a pressing need to develop and utilize data assimi ration techniques not only for operational use in specifying and forecasting the space environment but also to provide the tools to tackle key science questions. The modest level of support from the NSF base pro- grams (CEDAR, GEM, SHINE) and NASA SR&T has been inadequate to build comprehensive, systems-level mod- THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS els. Rather, individual pieces have been built, and first stages of model integration achieved with funding from such programs as NASA's ISTP program and its Sun- Earth Connections Theory Program (SECTP), the AFOSR MU RI program, NSF Science and Technology Center programs, and the multiagency support to such efforts as the Community Coordinated Model ing Center. Such pro- grams enable the development of theory and modeling infrastructure, including models to address the dynamic coupling between neighboring geophysical regions. Their value to the research community is clearly their provision of longer-term funding, which has been essen- tial to developing a comprehensive program outside the purview of SR&T. 10. The development and utilization of data assimila- tion techniques should be enhanced to optimize model and data resources. The panel endorses support for theory and model development at the level of the NASA Sun-Earth Connections Theory Program, the AFOSR/ ONR MURI program, NSF Science and Technology Center programs, and the multiagency support to such efforts as the Community Coordinated Modeling Cen- ter (CCMC). Support should be enhanced for large- scope, integrative modeling that applies to the cou- pling of neighboring geophysical regions and physical processes, which are explicit in one model and implicit on the larger scale. The preceding science recommendations can be grouped into three cost categories and prioritized (see Table 3.11. Equal weight is given to STP and LWS lines, as indicated by funding level. Smal I programs are ranked by resource allocation, while the Advanced Modular Incoherent Scatter Radar is the highest priority moderate initiative at lower cost than others. 3.1 INTRODUCTION Earth, unique in the universe as the only object known to support life, follows an orbit in the outer at- mosphere of the Sun an outer atmosphere that is con- tinually being explosively reconfigured. During these events, Earth is engulfed in intense high-frequency ra- diation, vast clouds of energetic particles, and fast plasma flows with entrained solar magnetic fields. Even though only a small fraction (generally <10 percent) of this energy penetrates into geospace, its effects are dra- matic.

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS TABLE 3.1 Panel's Recommended Priorities for New Initiatives Initiatives in Geospace Major SolarTerrestrial Probes (2) Living With a Star Discovery (1) Moderate Advanced Modular Incoherent Scatter Radar and Lidar Facilities Explorer Program (assume 3 missions in the 10 years will be devoted to AIM) L1 Monitor (excluding tracking) Small Instrument Distributed Ground- Based 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) Theory Living With a Star (geospace) Sun-Earth Connection Theory Program (geospace) DOD MURI (ionosphere) NSF STC (geospace) HPCC (geospace) NOAA, DOE/LANL, and DOD science for the A-l-M community 50 Subtotal 848 300 200 135 138 60 18 20 20 20 Total 3,065 To date, space science programs have provided detai led understanding of the average behavior of the component parts of geospace, in effect providing climat- ologies upon which to base educated guesses about the dynamic behavior of the global system. To go beyond this and understand the coupling processes and feed- back that define the instantaneous response of the glo- bal system is much more difficult. The A-l-M system occupies an immense volume of space. At the same time, processes on scale sizes from micro to macro im- pact the global system response. The ISTP program is the most ambitious program to date to explore the A-l-M system. ISTP samples the huge volume of the A-l-M system by simultaneous measure- ments from a handful of satellites. Despite the sparse a 1 33 coverage, analysis of data from ISTP satellites has al- lowed scientists to begin to glimpse the rich variety of coupling and feedback processes that define the global response of the geospace environment to solar wind disturbances. The first experiments with innovative im- aging technologies that view large regions of geospace in snapshots (e.g., from the IMAGE spacecraft) have al- ready provided insights into the instantaneous response, unattainable by past missions. The first attempts to achieve the high spatial and temporal resolution needed to survey the microscale controls of the global system (e.g., from the FAST spacecraft) have revealed new de- tails about acceleration processes and electrodynamic coupling. With these new missions, we are replacing our steady-state view of geospace regions with a dy- namical view. But we are far from understanding the complex coupling processes and interplay between components that dictate the integrated global system response. It is clear that the A-l-M system actively responds to the solar wind and that components of this system may be preconditioned or may interact in ways that redistrib- ute solar wind energy throughout the system, actively limiting the entry of solar wind energy into geospace during extreme events. A few examples are given in the next pages to illustrate the complexity of this interaction and the challenges that lie ahead. Life on this planet is protected from the high-energy radiation and dangerous particle clouds in interplan- etary space because Earth has its own magnetic field and is surrounded by an absorbing atmosphere. Earth's magnetic field presents a northward-directed magnetic field barrier to the oncoming solar wind in the ecliptic plane (Figure 3.1~. This barrier can be breached, how- ever, if southward-d i rected sol ar magnetic fields i mpact it and merge or reconnect with Earth's magnetic field. Fortunately, strongly southward-directed magnetic fields are not a persistent feature of the quiet interplanetary medium. They are mainly confined to structures gener- ated in explosive solar events and in high-speed plasma streams. The passage of southward interplanetary magnetic field (IMP) structures by Earth pumps energy into the near-space environment. The tightly coupled nature of the A-l-M system is clearly revealed by its response to interplanetary magnetic clouds (IMCs), which have strong and long-lived southward magnetic fields and drive the most intense magnetic storms. Intense convec- tion is produced, which brings particles from the mag- netotail storage region (called the plasma sheet) deep into the inner magnetosphere on open drift paths, ener-

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1 34 THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS FIGURE 3.1 (a) A schematic of the magnetosphere showing major particle populations and current systems; (b) close-up of radiation belts (trapped particles), including inner and outer zone populations and trapped anomalous cosmic rays (interstellar matter).

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS Sizing them to form the storm-time ring current, shown schematically in Figure 3.1. Under extreme conditions, the strong current produced by these particles cannot close upon itself in the equatorial plane (to form the ring of current that its name implies) but is forced to close through the subauroral and midlatitude ionosphere. This closure produces a strong electric field in the ionosphere called a polarization jet. The electric fields in the polar- ization jet map upward along the field lines to the mag- netosphere, producing a penetration electric field in the inner magnetosphere, further changing the drift paths of the ring-current ions. The plasmasphere (corotating plasma of ionospheric origin) responds strongly to the penetration electric fields and enhanced convection. Long plumes of plasmaspheric material snake out to the dayside magnetopause, draining thermal plasma into the dayside boundary layers. This plasma may later become a source for the plasma sheet (Figure 3.11. Along drift paths mapped into the ionosphere, storm-enhanced ion- ization moves toward the dayside polar cap, where geo- magnetic field lines connect to the interplanetary mag- netic field. Steep plasma density gradients at the edges of ionospheric density patches form in the changing con- vection pattern, playing havoc with technologies like the Global Positioning System, and ionospheric irregu- larities form, disrupting communication systems. There are indications that the ionosphere may, in turn, have a major impact on the dynamics of the mag- netosphere. Solar wind dynamic pressure variations trig- ger ionospheric outflows from the vicinity of the polar cap. These ionospheric "mass ejections" begin well be- fore the storm maximum, preconditioning the tail plas- mas with heavy ionospheric ions energized by the solar wind interaction. Enhanced convection during magnetic storms stresses the magnetotail, producing dramatic re- configurations of the basic structure of the magnetotail, called substorms. Auroral currents associated with sub- storms also produce an outflow of ionospheric ions di- rectly into the magnetotail. 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. Since this accelerated plasma drifts earth- ward under conditions of strong convection to form the ring current, there is a clear connection between mag- netotail dynamics and magnetic storm effects in the near- Earth region of the magnetosphere. Variations in plasma sheet density play an important role in modulating mag- netic storm intensity and substorm processes and repre- 1 35 sent another means by which the A-l-M system inter- nally modulates the geo-effectiveness of solar wind dis- turbances. The interplay between removal of plasma sheet material and refilling of the plasma sheet from the solar wind and the ionosphere to supply the ring current during storms is not understood. Even the basic mecha- nisms for refilling the plasma sheet (Figure 3.1 ) have not yet been determined. Earth's outer magnetosphere is often populated to a surprising degree by relativistic electrons, which pose a radiation hazard to space-based systems. The origin of the multi-MeV electrons in the outer zone is not known. They are generally correlated with increased substorm activity driven by high-speed solar wind and favorable coupl ing to southward interplanetary magnetic field, both of which have semiannual and solar-cycle varia- tions. Enhancements occur with relatively regular 27- day periodicity during the declining phase of the 11- year sunspot cycle and are wel I associated with high-speed solar wind stream structures. Flux variations at the solar activity maximum are dominated by coronal mass ejections (CM Es) (see the report of the Panel on Solar-Heliospheric Physics), which launch magnetic clouds toward Earth, producing geomagnetic storms. The mechan ism~s) by wh ich magnetospheric particles are accelerated to relativistic energies are unknown at present, although a number of interactions with plasma wave modes are promising candidates. The impact of solar wind shock structures on Earth's magnetosphere has been shown to generate induction-electric-field pulses that rapidly accelerate electrons and protons, gen- erating an entire new radiation belt in a matter of min- utes. An interesting coupling between the ring current and radiation belts results wherein magnetic fields gen- erated by the ring current cause scattering and loss of radiation belt particles. In addition, waves near the ion gyrofrequency generated by ring-current ions are be- lieved to contribute to electron precipitation losses in the dusk sector. Dramatic losses from the electron radia- tion belts (Figure 3.1b) also result from interaction of energetic electrons with lightning-generated waves, cal led whistlers. Lightning-induced electron precipita- tion events exemplify direct coupling of tropospheric weather systems with the radiation belts and the iono- spheric regions overlying thunderstorms. Much of the energy and momentum entering Earth's environment eventually finds its way into the upper at- mosphere. The in situ absorption of solar EUV radiation not on Iy protects I ife on Earth, but drives large day-night temperature and tidal wind variations in the upper at- mosphere, which vary dramatically with the solar cycle.

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1 72 coveri ng d iverse regions i n geospace, new i Information technologies are required to improve data access from a single coordinating site, to allow remote searching of these distributed data sets, and to simplify data assimila- tion into global models in real time and for postevent analysis. I Improvements i n meteorological weather forecast- ing have demonstrated the utility of adopting sophisti- cated data assimilation techniques. It is essential thatthe space physics and aeronomy communities learn, further develop, and implement these methods for both opera- tional and scientific use. The potential benefit of new observing systems can come to fruition only if maxi- mum use is made of the data; this, in turn, will happen only if a comprehensive data assimilation program is developed. This is not a trivial task, and the effort in- volved shou Id not be underestimated. Assimi ration mod- els can also provide the tools to visualize a wide net- work of data and provide guidance on when and where to target observations to ensure efficient use of resources. Data assimilation is the optimal combination of data with the physical understanding embedded in physical models. It is distinct from data synthesis, where a small number of observations are used to adjust a model out- put. 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 develop- ment that are needed to implement A-l-M objectives on future missions efficiently. The needed technology splits into two areas: spacecraft subsystems and instrumenta- tion. Both areas require active funding by NASA to fos- ter improvement. It should be emphasized that the best return on NASA's investment will come from a peer- reviewed competition open to universities and industry as well NASA centers. In the case of spacecraft sub- systems, the return will be immediate and far-reaching. Improvements in telemetry, command and data han- dling (CDH), attitude control, and power systems can be directly transferred to private industry, where they will make American spacecraft more competitive in a global economy. Instrumentation development has a less direct impact, but the innovations that come from better scien- tific instruments often lead the way for incorporating new technology into spacecraft subsystems. It is im- portant to realize that developments in these areas must support traditional, highly instrumented spacecraft as THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS well as smaller, more simply instrumented spacecraft (micro- and nanosatel I ites). Future NASA space science missions will increas- ingly rely on a multispacecraft approach, as is amply discussed in this report and those of the other panels. For such missions to be achieved at reasonable cost, spacecraft subsystems must become more efficient in their use of mass and power. For every scientific space- craft built in recent memory, the majority of mass and power go to spacecraft subsystems, not instrumentation. To improve the performance of these systems, NASA will need to foster research and innovation. Develop- ment of highly power-efficient CDH systems with good flexibility and increased-capacity mass memories with small impact on spacecraft resources will be critical to these missions. NASA is currently working on high-effi- ciency thruster systems. Multispacecraft missions can require frequent station keeping to maintain optimum spacecraft positioning; more efficient thrusters can have a direct impact on spacecraft size and mission longevity. This work should be continued and expanded. Both power generation and power storage improve- ments are needed. Although solar cells have become more efficient, development of still higher efficiency solar cells should be encouraged. For planetary mis- sions to the outer solar system, radioisotope thermal generators (RTGs) are needed. The development and use of RTGs is a politically sensitive issue, but if NASA is to continue exploration of Jupiter and beyond, these power sources must be developed so that the public is satisfied that they are safe. Without safe, politically ac- ceptable RTGs, exploration of the solar system and be- yond will be significantly limited. Battery development should also be encouraged. By decreasing the mass re- quirements for a given amount of stored power, smaller, more efficient spacecraft can be constructed. Multispacecraft missions will also place significant new demands on telemetry reception capacity. Much of this reception capacity is currently contained within the Deep Space Network (DSN). However, the DSN, as pres- ently configured, consists of relatively large, expensive receiving antennas. Recent experiences with Cluster and other missions suggest that DSN is stretched very thin. The next generation of multispacecraft missions will not fly at extremely large distances from Earth; most are envisioned to be within its magnetosphere. This sug- gests that NASA should consider augmenting the DSN with arrays of smaller, less-expensive antennas that can handle missions that stay within 20-30 RE of Earth. If each of the main DSN stations (Canberra, Goldstone, Madrid) had two, three, or four smaller dishes, then the

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS upcoming multispacecraft missions could have their te- lemetry reception offloaded onto these smaller dishes, freeing the larger ones for planetary or other low-signal- level missions. As part of making such a system efficient, automation of receivers must be considered to reduce operating costs. NASA should develop options for man- aging data reception to find solutions that will give effi- cient and sufficient capacity. On the instrumentation side of new technology, the key is to provide funding to scientists to develop the instrumentation. This support must be for the develop- ment of new basic technologies and materials as well as specific instrumentation designs. As an example, basic research in magnetoresistive materials may lead to new, highly efficient magnetometers. However, we also need novel designs for electrostatic detector optics to improve the efficiency of detection of low- and mid-energy ion mass analyzers. In the current environment, instru- mentation innovation does occur, but it tends to be spo- radic, and nonuniversity groups that have internal over- head return tend to be favored, because they can internally finance modest development efforts. By pro- viding steady, regular funding for instrument develop- ment that is openly competed for and peer-reviewed, along with support for suborbital and UNEX-class flight opportu n ities, NASA wi I I al I ow researchers to cou nt on continuing funding for their efforts to come up with new detector designs that wi 11 measure more accurately and more efficiently. An important part of the development of new, com- pact systems for both instrumentation and spacecraft is the microelectronics that is at the heart of these systems. Central to microelectronics is the development of mod- ern parts with good radiation tolerance. In particular, NASA must foster the development of red-hard micro- processors, programmable gate arrays, and other digital and analog electronic components so that the United States can remain competitive with the rest of the world. 3.6 RECOMMENDATIONS Future research in atmosphere-ionosphere-magneto- sphere science must prominently support projects, theo- ries, and models that address the three-dimensional, dynamic behavior of the coupled A-l-M system. Crucial to understanding dynamic, complex geophysical phe- nomena such as magnetic reconnection, auroral pro- 1 73 cesses, and electrodynamic ionosphere-thermosphere coupling are measurements from multiple platforms (e.g., the recently launched four-satellite Cluster 11 mis- sion and the planned Magnetospheric Multiscale mis- sion). Also critical to achieving such understanding are advances in the area of numerical simulation, including the development of mature coupled ionosphere models and the incorporation in global models of proper physi- cal representations of sub-grid-scale effects. Future measurements and models must pay even greater attention to these essential aspects of near-Earth space. The overarch i ng goal s are these: 1. To understand how Earth's atmosphere couples to its ionosphere and its magnetosphere and to the atmo- sphere of the Sun and 2. To attain a predictive capability for those pro- cesses in the A-l-M system that affect human ability to live on the surface of Earth as well as in space. We currently have a tantalizing glimpse of the physi- cal processes controlling the behavior of some of the individual elements in geospace. We must now address cross-cutting science issues, which include the instantaneous global system response of the A-l-M system to the dynamic forcing of the solar atmo- sphere. 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? In view of the multiple temporal and spatial scales we must understand the role of micro- and mesoscale processes in controlling the global-scale A-l-M system. The exchange of mass, momentum, and energy between the geophysical domains (e.g., connection of solar wind plasma at the magnetopause, ionospheric outflow, up- ward propagation of electromagnetic and mechanical energy from the lower atmosphere) is a key element in the coupled A-l-M system. It is now imperative that we understand the degree to which the dynamic coupling be- tween the geophysical regions controls and impacts the active state of the A-l-M system.

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1 74 The Sun is now recognized as one of the important factors in global change. Accordingly, we must resolve the physical processes that may be responsible for the solar forcing of climate change. These critical science issues thread the artificial bound- aries between the discipl ines, but within each discipl ine, important science questions remain. For example, Earth's outer magnetosphere, acting as a powerful par- ticle accelerator, is often populated by a surprising de- gree of relativistic electrons that pose a radiation hazard to space-based systems. It is important that we deter- mine the origin of the multi-MeV electrons in the outer magnetosphere and the cause of the pronounced fluctuations in their intensity. In the thermosphere and ionosphere, one of the funda- mental science issues that must be resolved is to deter- mlne the balance between internal and external forc- ing in the generation of plasma turbulence at low lati- tudes. To accomplish our goals we note that simultaneous, multiplatform remote-sensing observations of the A-l-M system as well as in situ measurements are urgently needed in order to specify the many interconnected dy- namic, thermodynamic, and composition variables. As our understanding of the complexity of the thermo- sphere, ionosphere, and magnetosphere grows, so does the requirement to capture observations of these mul- tiple facets of the coupled media. In the next decade, NASA should give highest prior- ity to multispacecraft missions such as Magnetospheric Multiscale (MMS) (Box 3.1), Geospace Electrodynamics Connections (GEC), Magnetospheric Constellation (Mag- Con), and Living With a Star's geospace missions, which take advantage of adjustable orbit capability and the advancing technology of small spacecraft. Missions that involve large numbers of simply instrumented space- craft are needed to develop a global view of the system and should be encouraged. NSF, for its part, should sup- port extensive ground-based arrays of instrumentation to give a global, time-dependent view of this system. Ground- and space-based programs should be coordi- nated as, for example, is being done in the Thermo- sphere-lonosphere-Mesosphere Energetics and Dynam- THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS ics (TIMED)/CEDAR program to take advantage of the complementary nature of the two distinct viewpoints. NASA, NSF, DOD, and other agencies should encour- age the development of theories and models that sup- port the goal of understanding the A-l-M system from a dynamic point of view. Furthermore, these agencies should work toward the development of data analysis techniques, using modern information technology, that assimilate the multipoint data into a three-dimensional, dynamic picture of this complex system. Funding for the NASA Supporting Research and Technology (SR&T) pro- gram should be doubled to bring the proposal success rate up from 20 percent to the level found in other agen- cies. SolarTerrestrial Probe (STP) flight programs should have their own targeted postlaunch theory, modeling, and data analysis support. MAJOR NSF INITIATIVE Simultaneous, multicomponent, ground-based ob- servations of the A-l-M system are needed in order to specify the many interconnecting dynamic and thermo- dynamic variables. As our understanding of the com- plexity of the A-l-M system grows, so does the require- ment to capture observations of its multiple facets. The proposed Advanced Modular Incoherent Scatter Radar (AMISR) (Box 3.2) will provide the opportunity for coor- dinated radar-optical studies of the aurora and coordi- nated investigations of the lower thermosphere and me- sosphere, a region not well accessed by spacecraft. Initial location at Poker Flat, Alaska, will allow coordi- nation of radar with in situ rocket measurements of au- roral 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. 1. The National Science Foundation should extend its major observatory component by proceeding as quickly as possible with Advanced Modular Incoherent Scatter Radar (AMISR) and by developing one or more lidar- centered major facilities. Further, the NSF should begin an aggressive program to field hundreds of small auto- mated instrument clusters to allow mapping the state of the global system. Ground-based sensors have played a pivotal role in our understanding of A-l-M science and must continue to do so in the coming decade and beyond. Anchored by a state-of-the-art, phased-array scientific radar, the $60 million AMISR is a crucial element for A-l-M. A distributed array of instrument clusters would provide

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS 1 75 The Magnetospheric Multiscale (MMS) mission is a multispacecraft Solar Terrestrial Probe to study magnetic reconnection, charged particle acceleration, and turbulence in key boundary regions of Earth's magnetosphere. These three processes which control the flow of energy, mass, and momentum within and across plasma boundaries occur throughout the universe and are fundamental to our understanding of astrophysical and solar system plasmas. Only in Earth's magnetosphere, however, are they readily accessible for sustained study through the in situ measu remeet of plasma properties and of the electric and magnetic fields that govern the behavior of the plasmas. But despite four decades of magnetospheric research, much about the operation of these fundamental processes remains unknown or poorly under- stood.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 magneto- pause to the high-latitude magnetopause, and from the near tail to the distant tail. Adjustable interspacecraft separa- tions from 10 km up to a few tens of thousands of kilometers will allow the cluster to probe the microphysical aspects of reconnection, particle acceleration, and turbulence and to relate the observed microprocesses to larger-scale phenom- ena. MMS will uniquely separate spatial and temporal variations over scale lengths appropriate to the processes being studied down to the kinetic regime beyond the approximations of MHD. From the measured gradients and curls of the fields and particle distributions, spatial variations in currents, densities, velocities, pressures, and heat fluxes will be calcu- lated. In order to sample all of the magnetospheric boundary regions, MMS will employ a unique four-phase orbital strategy involving carefully sequenced changes in the local time and radial distance of apogee and, in the third phase, a change in the inclination of the orbit from 10 degrees to 90 degrees. In the first two phases, the investigation will focus on the near- Earth tail and the subsolar magnetopause (Phase 1; 12 RE apogee) and on the low-latitude magnetopause flanks and near- Earth neutral line region (Phase 2; apogee increasing from 12 to 30 RC). In Phase 3, MMS will use a lunar Gravity assist to C, , ~ - -, achieve a deep-tail orbit with apogee at 120 RE and to effect the inclination change to 90 degrees. In this phase, MMS will study plasmoid evolution and reconnection at the distant neutral line. In the final, high-inclination phase, perigee will be increased to 10 RE and apogee reduced to 40 RE on the night side, and the MMS cluster will skim the dayside magneto- oause from pole to pole, sampling reconnection sites at both low and high latitudes. The nominal MMS mission has an operational duration of 2 years.While some mission-enhancing technologies such as an interspacecraft ranging and alarm system are desirable, no new mission-enabling technologies are required for the successful accomplishment of the MMS science objectives. MMS is a mission of both exploration and understanding. Its primary thrust is to study on the mesa- and microscales the basic plasma processes that transport, accelerate, and energize plasmas in thin boundary and current layers the processes that control the structure and dynamics of the magnetosphere. With sensitive instrumentation and variable spacecraft orbits and interspacecraft spacing, MMS will integrate for the first time observations and theories over all geomagnetic scale sizes, from boundary layer processes that operate at the smallest scale lengths to the mesoscale dynamics that couple solar wind energy throughout the Earth's space environment. The major science goals of the MMS mission include an understanding of the following: Reconnection at the magnetopause at high and low latitudes, Reconnection in the magnetotail and the associated magnetotail dynamics, Plasma entry into the magnetosphere, Physics of current sheets, Substorm initiation processes, and Cross-scale coupling between micro- and mesoscale phenomena.

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1 76 THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS The Advanced Modular Incoherent Scatter Radar (AMISR) is a state-of-the-art phased-array incoherent scatter radar (ISR).This highly versatile instrument will be ringed by less expensive complementary systems, typically optical in nature. The science plan is to target unsolved problems in aeronomy by placing AMISR in appropriate geographic locations for periods of 3 to 5 years.The first science goal is to understand the coupling between the neutral atmosphere and the high- speed current-carrying plasma in the auroral oval.This interaction involves electrodynamic forcing via momentum transfer from the plasma to the neutrals,Joule heating due to the currents that flow, composition changes of the thermosphere, and particle impact ionization associated with the aurora, to name just a few aspects.The first AMISR site will be in the Fairbanks area to take advantage of existing instrumentation and the Poker Flat Rocket Range. Subsequent sites will be decided on the basis of community input by a panel of research scientists. Candidates include a location in the deep polar cap,which has never been studied using the ISR technique,and a location in the off-equatorial zone to study development of the ionospheric anomaly and its severe effects on communications systems. 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. Alterna- tively, the faces can be deployed separately since each is in its own right a very powerful system. A complementary set of optical- and radiowave-based sensors will accompany the deployment of the AMISR and extend its capabilities. The design of the AMISR is completed and a prototype element has been constructed and tested successfully. Once the project is approved, a first face can be constructed in about 2 years. Subsequent faces will be online in about the same time scale.The total cost is $60 million, including the associated additional instrumentation. the high temporal and spatial resolution observations needed to drive the assimilative models, which the panel hopes will parallel the weather forecasting models we now have for the lower atmosphere. Much of the neces- sary infrastructure for such a project has already been demonstrated in the prototype Suominet, a nationwide network of simple Global Positioning System/meteorol- ogy stations linked by the Internet. The proposed pro- gram would add miniaturized instruments, such as all- sky imagers, Fabry-Perot interferometers, very-low- frequency receivers, passive radars, magnetometers, and ionosondes in addition to powerful GPS-based systems in a flexible and expandable network coupled to fast, real-time processing, display, and data distribution ca- pabilities. Instrument clusters would be sited at universi- ties and high schools, providing a rich hands-on envi- ronment for students and training with instruments and analysis for the next generation of space scientists. Data and reduced products from the distributed network would be distributed freely and openly over the Internet. An overall cost of $100 million over the 1 O-year plan- ning period is indicated. Estimated costs range from $50,000 to $150,000 per station depending on the in- struments to be deployed. Adequate funding would be included for the development and implementation of data transfer, analysis, and distribution tools and facili- ties. Such a system would push the state of the art in information technology as well as instrument develop- ment and miniaturization. Extendi ng the present radar-centered upper atmo- spheric observatories to include one or more lidar-cen- tered facilities is crucial if we are to understand the boundary between the lower and upper atmosphere. Fortunately, a number of military and nonmilitary large- aperture telescopes may become avai fable for transition to lidar-based science in the next few years. Highest priority would be given to a facility at the same geo- graphic 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 geo- space environment just as the Discovery program now provides opportunities in planetary science. The contin- ued opportunities for University-Class Explorer (UNEX) (Box 3.3), Small Explorer (SMEX), and Medium-Class Explorer (MIDEX) missions, practically defined in terms of their funding caps of $1 4 mi l l ion, $90 mi l l ion, and $180 million, allow the community the greatest creativ- ity in developing new concepts and a faster response time to new developments in both science and technol- ogy. These missions also provide a crucial training grou nd for graduate students, managers, and engi neers.

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS 1 77 Small spacecraft missions can be extremely productive scientifically and can also provide a fertile training ground for students of science and engineering. NASA has attempted to establish several new lines of small-end missions, including the UNEX mission line in space science. Of course, the Small Explorer (SMEX) program (at a larger scale size and cost) has been a remarkable success, and the smaller sounding rocket and balloon programs have in the past been immensely rich and rewarding programs. In carrying out the Student Explorer Demonstration Initiative (STEDI) program,the Universities Space Research Association set an excellent tone for how to manage small missions. Appropriate levels and numbers of reviews were employed and key types of help were provided to STEDI teams, as needed. It has been widely acknowledged that small-spacecraft missions can provide a profound educational experience for university students. It has been from the ranks of such highly trained students that many present-day principal investiga- tors of NASA space science missions have emerged.To have a future space science program with strong experimental content, the United States must ensure that student training continues to be a high priority. This demands that small, focused spacecraft missions be available to the university research community,which in turn means that an ample number of spacecraft payloads must be made available to researchers. The NASA UNEX program was generally viewed as a direct successor to the STEDI program. However, UNEX has been effectively cut from future NASA budgets. It is regrettable that this program and the opportunities afforded by the STEDI concept will not be available to university scientists for research and educational opportunities. 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. NASA and other agencies could serve the university community in a most beneficial and effective way if they would offer low-cost launch possibilities to university groups. This would allow the community to revivify the UNEX program, establish appropriate small-spacecraft launch capabilities, strengthen the engineering and science education program, and fully develop this nation's small satellite program potential. In carrying out these steps, the agencies would perform an immense service for university researchers throughout the nation. At a cost of ~$20 million per mission and with launches once or so per year, the program would make very modest resource demands. NRC. 1994. A Space Physics Paradox: Why Has Increased Funding Been Accompanied by Decreased Effectiveness in the Conduct of Space Physics Research? National Academy Press,Washington, D.C. Imager for Magnetopause-to-Aurora Global Exploration (IMAGE), launched in March 2000,is an example of a highly successful MIDEX mission; it was preceded by the first two ongoing SMEX missions, Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) and FastAuroral Snapshot Explorer (FAST), launched in 1992 and 1996, which have provided enormous scientific re- turn for the investment. The Aeronomy of Ice in the Mesosphere (AIM) SMEX was recently selected for launch in 2006. The UNEX program, after the great suc- cess of the Student Nitric Oxide Explorer (SNOE), launched in February 1998, has effectively been can- celled. This least expensive component of the Explorer program plays a role similar to the sounding rocket pro- gram, with higher risk accompanying lower cost and a great increase in the number of flight opportunities. An increase in funding to $20 million per mission with one launch per year would make this program viable with modest resources. 2. The SMEX and MIDEX programs should be vigor- ously maintained and the U N EX program should quickly be revitalized. The Solar Terrestrial Probe (STP) line of missions defined in the NASA Sun-Earth Connection (SEC) Road- map (strategic planning for 2000 to 2025) has the poten- tial to form the backbone of A-l-M research in the next decade. The missions that are part of the current pro- gram includeTIMED, launched in February 2002, Solar- B, Solar Terrestrial Relations Observatory (STEREO), MMS, G KC, and MagCon. After TIMED, launched in February 2002, the next A-l-M/STP mission, MMS, is in the process of instrument selection for a 2009 launch.

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1 78 The STP cadence, with one A-l-M mission per decade (TIMED was significantly delayed), has fallen behind the NASA SEC Roadmap projections. 3. The panel heartily endorses the STP line of missions and strongly encourages an increase in the launch ca- dence, with GEC and MagCon proceeding in parallel. The A-l-M research community has very success- fully utilized the infrastructure developed within the ISTP program. The integration of the data from spacecraft and ground-based programs beyond those funded by the ISTP project itself such as those of NOAA, LANE, and the DOD have contributed substantially to our under- standing of the global system. Comparisons between the Sun-Earth system and other Sun-planet or stellar-planet systems provide im- portant insights into the underlying physical and chemi- cal processes that govern A-l-M interactions. Improved understanding of A-l-M coupling phenomena such as planetary and terrestrial auroras would benefit from such an approach. 4. The Sun-Earth Connection program partnership with the NASA Solar System Exploration program should be revitalized. A dedicated planetary aeronomy mission should be pursued vigorously, and the Discovery pro- gram should remain open to A-l-M-related missions. NASA SUBORBITAL PROGRAM The NASA Suborbital program has produced out- standing science throughout its lifetime (Box 3.4~. Many phenomena have been discovered using rockets, rock- oons, and balloons, and many outstanding problems brought to closure, particularly when space-based fa- cilities are teamed with ground-based facilities. These phenomena include the auroral acceleration mecha- nism, plasma bubbles at the magnetic equator, the charged nature of polar mesospheric clouds, and mono- energetic auroral beams. This program continues to gen- erate cutting-edge science with new instruments and data rates that are more than an order of magnitude greater than typical satellite data rates. Both unique alti- tude ranges and very specific geophysical conditions are accessible only to sounding rockets and balloons, particularly in the campaign mode. Many current satel- lite experimenters were trained in the Suborbital pro- gram, and high-risk instrument development can occur only in such an environment. To accomplish significant training, it is necessary that a graduate student remain in THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS a project from start to finish and that some risk be ac- ceptable; both are very difficult in satellite projects. The high scientific return, coupled with training of future generations of space-based experimenters, makes this program h igh Iy cost-effective. The sounding rocket budget has been level-funded for over a decade, and many principal investigators are discouraged about the poor proposal success rate as well as the low number of launch opportunities. The sounding rocket program was commercialized in 2000; in this changeover, approximately 50 civil service posi- tions were lost and the cost of running the program increased. Approved campaigns were delayed by up to a year, and it is not yet clear whether the launch rate will ever return to precommercialization levels. Effectively, commercialization has meant a significant decline in funding for the sounding rocket program. An additional concern is that, as currently structured i.e., with a fixed, 3-year cycle for all phases of a sounding rocket project funding is not easily extended to allow gradu- ate students to complete their thesis work, because it is generally thought that such work should fall under the SR&T program, already oversubscribed. The rocket pro- gram has a rich history of scientific and educational benefit and provides low-cost access to space for uni- versity and other researchers. Further erosion of this pro- gram will result in fewer and fewer young scientists with experience in building flight hardware and will ulti- mately adversely affect the much more expensive satel- lite programs. 5. The Suborbital program should be revitalized and its funding should be reinstated to an inflation-adjusted value matching the funding in the early 1980s. To fur- ther 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 well- established effects of space weather variations on tech- nology and the less clear yet tantalizing influence of solar variability on climate. The societal impacts of space weather are broad commun ications, navigation, human radiation hazards, power distribution, and satel- lite operations are all affected. Space weather is of in- ternational concern, and other nations are pursuing par- allel activities, which could be leveraged through

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS 1 79 NASAL Suborbital program provides regular, inexpensive access to near-Earth space for a broad range of space science disciplines, including space plasma physics, astronomy, and microgravity. The program has been extremely successful throughout its history, consistently providing high scientific return for the modest funding invested. Phenomena from auroral physics to supernovae have been investigated with sounding rocket and balloon experiments, and many key discoveries in these fields have come from this program. For the science of lower-altitude regions such as equatorial ionospheric irregularities and mesospheric physics, this program provides the only access because these regions are too high for airplanes and too low for satellites. Moreover, the use of new, advanced instrumentation concepts coupled with data rates that exceed those of satellites by a factor of more than 10 have provided measurements of a resolution and quality that are simply unobtainable elsewhere.This science is exciting and central to NASAL mission. The program also has a spectacular track record in training future scientists and engineers. More than 300 Ph.D.theses have been based on rocket data alone.This has provided a regular flow of technically adept individuals who have first- hand experience in building space flight instrumentation. Indeed, most of today's successful satellite experimenters were trained in this program.The experience that students receive developing, flying, and interpreting data from instruments they themselves have built is only possible within this program.This is an unparalleled learning experience that satellite programs cannot match because they are too risk-averse and span too long a period for a graduate student to be involved from start to finish. Despite this tremendous track record in which the Suborbital program has continually demonstrated its scientific validity (made clear through a series of reviews over the past decade), funding for the program has seriously eroded. Its conversion to a government-owned, contractor-operated program, coupled with loss of many civil servant positions, has left the program severely underfunded for operations. Additionally, funding for scientific investigations has remained stagnant, resulting in a significant decline in the number of funded investigations over the past 15 years.There is -treat .~ , .~ .~ .~ , , .~ . . . . . . . . . . . . . . concern among the scientific community that NAbA management does not deem the program sutticlently Important to restore and protect its funding.This attitude must be changed and the program must be restored to a healthy level that will allow it to continue to play its important scientific and student training roles in which it is so uniquely effective.SeeA Space Physics Paradox for further discussion.3 NRC. 1994. A Space Physics Paradox: Why Has Increased Funding Been Accompanied by Decreased Effectiveness in the Conduct of Space Physics Research? National Academy Press,Washington, D.C. collaboration. The role of solar variability in climate change remains an enigma, but it is now at least being recogn ized as i mportant to ou r u nderstand i ng of the natural as opposed to anthropogenic sources of cli- mate variabi I ity. 6. To maximize the societal impact of studies and knowledge of the A-l-M system, the study of solar vari- ability both of its short-term effects on the space ra- diation environment, communications, navigation, and power distribution and of its effect on climate and the upper atmosphere should be intensified by both mod- eling and experimentation. NASA's Living With a Star program, as defined by the Science Architecture Team report, should be imple- mented, with increased resources for the geospace com- ponent. The share of resources required for the Solar Dynamics Observatory, already defined before the start of LOOS, has resulted in an unbalanced portfolio. Missions such as the National Polar-orbiting Opera- tional Environmental Satellite Systems (NPOESS) and Solar Radiation and Climate Experiment (SO RCE) should provide vital scientific data for monitoring long-term solar irradiance, and NPOESS should provide iono- sphere and upper atmosphere observations to fill gaps in measurements needed to understand the A-l-M system. An L1 monitor should be a permanent facility, to provide solar wind measurements crucial to determin- ing the response of the A-l-M system to its external driver. 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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1 80 NASA's new Living With a Star program can, over the next decade, provide substantial new resources to address these goals. It is crucial that there be overlap between the geospace and solar mission components of LWS for the A-l-M system to be studied synergistical Iy, that resources be adequate for the geospace compo- nent, and that theory, modeling, and the comprehensive data system that will replace the ISTP infrastructure be defined at the outset, as called for in the Science Archi- tecture Team report.2 The National Space Weather Pro- gram, a multiagency endeavor establ ished in 1 995, ad- dresses the potentially great societal impact of the physical processes from the Sun to Earth that affect the near-Earth environment in ways as diverse as terrestrial weather. The program specifically addresses the need to transition scientific research into operations and to assist users affected by the space environment. Such multiagency cooperation is essential for progress in pre- dicting response of the near-Earth space environment to short-term solar variabi I ity. Several potential mechanisms for a solar variability- climate connection have been suggested: (1 ) changes in the Sun's total irradiance or luminosity, which is the basic driver of the climate system; (2) changes in spec- tral irradiance, particularly in the UV, which drives the chemistry and dynamics of the middle atmosphere and has been shown by modeling studies to influence the dynamics of the troposphere; and (3) the possible influ- ence of cosmic-ray and electric-field variations on cloud nucleation, which could significantly modify Earth's ra- diation balance. 7. The NOAA, DOE/LAN L, and DOD operational spacecraft programs should be sustained and DOD launch opportunities should be utilized for specialized missions such as geostationary airglow imagers, auroral oval imagers, and neutral/ionized medium sensors. The interagency cooperation established in the NSWP is outstanding and is a model for extracting the maximum benefit from scientific and technical pro- grams. It has also been effective at bringing together different scientific disciplines and the scientific and op- erations communities. Interagency cooperation has 2NASA, Living With a Star, Science Architecture Team. 2001 . Report to the Sun-Earth Connection Advisory Subcommittee, August. Avail- able on I i ne at . THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS worked well in the AFOSR/NSF Maui Mesosphere and Lower Thermosphere Program, and it has been key to the success of the NOAA GOES and NPOESS programs of meteorlogical satellites with space environment moni- toring capabilities. International multiagency coopera- tion has been very successful for the ISTP program, which involves U.S., European, Japanese, and Russian space agencies. Global studies require such inter- national cooperation. The panel recognizes that much more science can be extracted by careful coordination of ground- and space-based programs. MAXIMIZING SCIENTIFIC RETURN Funding for NASA Supporting Research and Tech- nology, including guest investigator studies and focused theory, modeling, and data assimilation efforts, is essen- tial for maximizing the scientific return from large in- vestments in spacecraft hardware. Supporting Research and Technology While spacecraft hardware projects are concen- trated at relatively few institutions, the NASA SR&T program is the primary vehicle by which independent investigations can be undertaken by the broader com- munity. Likewise, NSF helps individual investigators to carry out targeted research through its Division of Atmo- spheric Sciences base programs SH I N E, CEDAR, and GEM. Such individual Pl-driven initiatives are the most inclusive, with data analysis as wel I as theoretical efforts and laboratory studies, and often lead to the highest science return per dollar spent. The funding for such program elements falls far short of the scientific oppor- tunities, with the current success rate for submitted NASA SR&T proposals being 10 to 20 percent. Further- more, limited available SR&T funds have been used for guest investigator participation in underfunded STP-class flight programs. Without adequate MO&DA funding for NASA orbital and suborbital programs, the SR&T budget intended for targeted research on focused scientific ques- tions has been utilized to support broader data analysis objectives. 8. The funding for the SR&T program should be in- creased, and STP-class flight programs should have their own targeted postlaunch data analysis support. 9. A new small grants program should be established within NSF that is dedicated to comparative atmo- spheres, ionospheres, and magnetospheres (C-A-I-M).

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PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS 1 81 The comparison of the Sun-Earth system to other Sun-planet systems can provide unique insights into how atmo- spheres, ionospheres, and magnetospheres (A-l-M) respond to solar inputs.The physical and chemical processes control- ling these responses manifest themselves very differently at each solar system body,yet are essentially the same at a basic level.AII the techniques that have been used so successfully to understand solar-terrestrial physics (e.g., modeling,ground- based and remote observations, and in situ measurements) 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). A new C-A-I-M grants program at NSF would play a key role in addressing the interdisciplinary issues needed to understand and relate A-l-M processes throughout our solar system, or even at other stellar systems. Such a grants pro- gram would provide much needed resources for analysis of both past and future data sets (from ground- or space-based observatories, or from in situ missions), modeling and data interpretation related to A-l-M objectives, telescope time, special meetings devoted to terrestrial-planetary issues, and the nonmission research support needed to encourage C-A-I-M science activities in the community. Such a grants program would need about $5 million per year in order to adequately develop and explore the linkages between the terrestrial and planetary manifestations of atmosphere- ionosphere-magnetosphere physics. A new C-A-I-M grants program at NSF (Box 3.5) such programs as NASAls ISTP and its Sun-Earth Con- would allow the techniques that have been applied so nections Theory Program, the AFOSR/ONR Multidisci- successfully to A-l-M processes at Earth (modeling, plinaryUniversityResearch Initative program, NSFSci- ground- and space-based observations, and in situ mea- ' - ' ' ^ ' ' surements) to be used to understand A-l-M processes at other planets. Such a comparative approach would im- prove understanding of these processes throughout the sol ar system, i ncl ud i ng at Earth. Presently, a modest $2 million Planetary Science program at NSF covers all of solar system science (except for solar and terrestrial stud- ies), with only a small fraction going to planetary A-l-M research. Theory, Modeling, and Data Assimilation Theory and modeling provide the framework for in- terpreti ng, understand) ng, and visual izi ng diverse mea- surements at disparate locations in the A-l-M system. There is now a pressing need to develop and utilize data assimi ration techniques not only for operational use in specifying and forecasting the space environment but also to provide the tools to tackle key science questions. The modest level of support from the NSF base pro- grams (CEDAR, GEM, SHINE) and NASA SR&T has been inadequate to build comprehensive, systems-level mod- els. Rather, individual pieces have been built and first stages of model integration achieved with funding from , , , ence and Technology Center programs, and the multiagency support for such efforts as the Community Coordinated Modeling Center. Such programs enable the development of theory and model ing infrastructure, including models to address the dynamic coupling be- tween neighboring geophysical regions. Their value to the research community is clearly their provision of longer-term funding, which has been essential to devel- oping a comprehensive program, outside the purview of SR&T. 10. The development and utilization of data assimila- tion techniques should be enhanced to optimize model and data resources. The panel endorses support for theory and model development at the level of the NASA Sun-Earth Connections Theory Program, the AFOSR/ ONR MURI program, NSF Science and Technology Center programs, and the multiagency support for such efforts as the Community Coordinated Modeling Center (CCMC). Support should be enhanced for large-scope, integrative modeling that applies to the coupling of neighboring geophysical regions and physical pro- cesses, which are explicit in one model and implicit on the larger scale.

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182 The preceding science recommendations are grouped into three cost categories and prioritized in Table 3.1. Equal weight is given to STP and LWS lines, as indicated by funding level. Small programs are ranked by resource allocation, while the Advanced Modular Incoherent Scatter Radar is the highest-priority moder- ate initiative at lower cost than others. BIBLIOGRAPHY GEM documents. Available online at . National Aeronautics and Space Administration (NASA), Office of Space Sciences. 2000. Strategic P/an. NASA, Wash i ngton, D.C. NASA. 2000. Sun-Earth Connection Roadmap, Strategic Planning for 2000-2020. NASA, Washington, D.C. NASA, Living With a Star, Science Architecture Team. 2001. Report to the Sun-Earth Connection Advisory THE SUN TO THE EARTH AND BEYOND: PANEL REPORTS Subcommittee, August. Available online at National Research Council (NRC). 2000. Radiation and the Internationa/ Space Station: Recommendations to Reduce Risk. National Academy Press, Washington, D.C. . NRC.1994. A Space Physics Paradox: Why Has Increased Funding Been Accompanied by Decreased Effectiveness in the Conduct of Space Physics Research? National Academy Press, Washington, D.C. National Science Foundation (NSF). 1995. National Space Weather Program: The Strategic P/an, FCM- P30-1995. Office of the Federal Coord i nator for Meteorology, Silver Spring, Md. NSF.1997. National Space Weather Program: The Implementation P/an, FCM-P31 -1997. Office of the Federal Coordinator for Meteorology, Silver Spring, Md. NSF. 1997. CEDAR Phase 111 Document. Available onl ine at .