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Appendixes The appendixes that follow are reports or excerpts of reports that resulted from workshops conducted by NASA In support of the present study. These efforts are an important part of the study and are included here in order to make the task group report complete. The four workshops were conducted by different organiza- tions and in different manners. Thus, the resulting reports are very different in character. What follows are four documents that represent, at least, the essential features of these reports: A. Workshop on Unaging of the Earth's Magnetosphere. This workshop was convened by the task group at the NAS Woods Hole study center during the task group meeting of July 1985. Appendix A represents the complete report. B. Jupiter Polar Orbiter Workshop. Appendix B is a sum- mary of the report of the workshop held at UCLA in July 1985. C. Workshop on Plasma Physics Research on the Space Sta- tion. Appendix C is taken from a review paper describing the results of the workshop held in May 1985 in Alabama. D. High-Resolution Observations of the Sun. Appendix D represents the complete report of the workshop held at the Na- tional Solar Observatory in Tucson, Arizona, in January 1986. 57

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Appendix A Workshop on Imaging of the Earth's Magnetosphere WORKSHOP PARTICIPANTS Lyle Broadfoot, University of Arizona Andrew Cheng, Johns Hopkins University/Applied Physics Laboratory Paul Feldman, Johns Hopkins University David Gorney, Aerospace Corporation Warren Moos, Johns Hopkins University Edward Roelof, Johns Hopkins University Donald Shemansky, University of Arizona Donald Williams, Johns Hopkins University/Applied Physics I.aboratory so

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60 CONTENTS A.1 ~troducUon, 61 AN Imaging of the Aurora Oval: Present Status and Future Needs, 64 A.3 Prospects far Extreme Ultraviolet Dogleg ~ Plums in the ~agnetospbere, 66 A.4 Prospects far Neutral Particle Imaging of Planetary ~agnetospberes, 72 A.S Conclusions and Recommendatlons, 77 l

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61 A.1 INTRODUCTION Our present knowledge about the structure of the Earth's magnetosphere has been formed over the years largely on the bash of local measurements from spacecraft that move along trajectories that are molated in space and time. However, even these limited observations show that the magnetosphere is essentially a dynamic system with large configuration changes driven both by direct variations in the solar wind and by more indirect processes that trigger large-ecale instabilities associated with substorms. Because of their enormous sizes and because there are large- scale variations in both space and time, planetary magnetospheres pose major challenges to scientists attempting to understand global behavior an understanding that ~ necessary in a program aimed at developing quantitative predictive models of these systems. Since single-po~nt observations from an molated satellite within the magnetosphere are obviously inadequate for this task, the ini- tial response to the challenge of studying global behavior has been to conduct sunultaneous multmatellite observations within the magnetospheric system. For example, the International Mag- netospheric Study (IMS) program was based on use of the ESA GEOS satellites in geostationary orbits, the NASA ISE~3 space- craft at the sunward libration powt, ~d the NASA-ESA space- craft ISE~1 and ISE~2 in the same elliptical orbit with apogee of 23 earth radii. This program was highly successful, and it provided definitive information on the structure of various thin boundaries and on localized plasma physics phenomenaa soccer due to the small reparation between ISE~! and ISE~2 and due to their coordinated observing schedules. However, the program was not nearly as successful in its thrust toward studies of global dynamics. This was due both to the lack of coordinated observing schedules for the primary IMS spacecraft and to the fact that the satellite trajectories were not chosen to optimize global studies. Thus, even after the IMS, a number of different theories ex- isted to explain global observations, but definitive choices could not always be made on the basis of available data. One example ~ the controversy between boundary layer and reconnection modem of substorm-related phenomena in the Earth's magnetotail. An- other example is the question of whether energy is stored for long periods in the magnetota~} and then released suddenly to cause a

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62 substorm, or whether a substorm is caused by a transient increase in energy input from the solar wind. Individual components of the magnetosphere such as the field- aligned current systems near the Earth, the plasma sheet distri- butions, and the high-energy radiation belts have been relatively well measured separately but are poorly understood as interact- ing parts of a whole. Fundamental controversies on the nature of global dynamic phenomena such as substorms are a natural re- sult. Indeed, significant advances have recently occurred in one of the areas cited above aurora and field-aligned currents near the Earth precisely because of the advent of global auroral imaging in the ultraviolet with simultaneous charged particle and magnetic field measurements on the Dynamic Explorer mission. Examples of these very significant observations are shown in Figure A.1. The International Solar-Terrestrial Physics (ISTP) program represents a major new thrust in our attempt to understand global magnetospheric dynamics. This program, specifically designed for global studies, will place appropriately instrumented satellites in key magnetospheric locations, and simultaneous auroral imaging will be utilized to obtain data on the magnetospheric energy de- position into the atmosphere. A strong theory, modeling, and computer simulation effort has been incorporated into ISTP from the beginning, thus assuring the development of global models to be used with the ISTP data base. Finally, since ISTP has been designed as a global studies program from the outset, the partic- ipating space agencies (NASA, the European Space Agency, and the Japanese Institute for Space and Astronautical Sciences) have agreed on full coordination of observing schedules to maximize simultaneous coverage from the ISTP spacecraft. They will also establish a common central data base facility through which all ISTP researchers will have access to all ISTP data. A major result of the ISTP program will involve the develop ment and initial qualitative testing of the first truly global mode! of the Earth's magnetosphere. More accurate tests will certainly be needed as the community attempts to move the modeling effort into a quantitative predictive phase. Ordinarily this requires a dense grid of observing platforms. However, for a system as vast as the terrestrial magnetosphere, it would not be economically feasible to provide a sufficiently dense grid using local spacecraft observations alone. A new and innovative approach is required,

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hL - ~ - FIGURE A.1 Ultraviolet auroral images from Dynamics Explorer.

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64 and recent measurements suggest that this approach should in- volve development of an imaging capability for the magnetosphere as a whole. This report summarizes the topics discussed at the Workshop on Imaging of the Earth's Magnetosphere, which was held at the NAS Study Center in Woods Hole, Massachusetts, on July 30 and 31, 1985, under the auspices of the Solar and Space Physics Task Group of the Space Science Board's study: Space Science in the Twenty-First Century. In the next section is a brief description of the science return from the present programs involving topside imaging of the auroral oval at atmospheric altitudes and expectations for improvement. The third section contains a discussion of the prospects for ex- treme ultraviolet imaging of the relatively dense and coo! plasma of the plasmsphere, magnetopause, bow shock, and storm-time plasma sheet. The use of energetic neutral (generated by charge exchange) for imaging of high-temperature plasma regions (e.g., the ring current and outer radiation belt) is discussed in the fourth section, and the conclusions and recommendations are contained in the final section. A.2 IMAGING OF THE AURORAL OVAL: PRESENT STATUS AND FUTURE NEEDS Auroral zone observations of visible, ultraviolet, and x-ray emissions generated by the precipitation into the atmosphere of energetic particles streaming downward along the geomagnetic field have provided extremely important means for remote sensing of dynamical phenomena that develop In the magnetosphere. The auroral region has been compared to a television screen that allows us to view the end effects of very remote magnetospheric processes. For years we looked upward toward the aurora from the ground and we were able to observe parts of the auroral displays, but the ground-based observations were limited" in space and they were also restricted to the visible part of the spectrum. Early results from the low-altitude polar-orbiting Defense Me- teorological Satellite Program (DMSP) provided a large data base of broadband visible auroral imagery. from this data set much was learned about the large- and small-scale morphology of the aurora, the response to changing conditions in the solar wind, and the occurrence of brief but energetic substorms. These early

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65 photographs from space were also very significant because they provided a medium to tie together other satellite and ground- based observations of the particles and fields responsible for and resulting from the aurora. A major drawback of these early oh servations was their scarcity the DMSP orbits provide auroral images with temporal separations of 90 min. The recent Dynamics Explorer (DE) satellite remedied this problem by imaging the aurora continuously from a high-altitude elliptical orbit. Figure A.l shows a set of examples from DE, taken consecutively at ultraviolet wavelengths. Auroral unages of this type are also available with somewhat diminished quality under sunlight illumination (as demonstrated by observations from the low-altitude HILAT spacecraft). We now have continuous global images from the auroral region, and they have yielded extremely significant new information on auroral forms and morphology. Scientifically, auroral imagery could provide even greater quan- titative information if sunultaneous multispectral Nonages were available. Such mult~pectral techniques are now being developed to derive quantitatively the characteristics of the perturbations of the neutral and ionized atmosphere due to the aurora. X-ray imaging of the aurora from space also offers promise for quantitative remote sensing of low-altitude processes since the x-ray emissions (bremsstrahIung) occur directly as a result of ener- getic auroral electrons colliding with atmospheric constituents. A number of successful imaging x-ray instruments have been flown in low-altitude polar orbit. Although the low-altitude observations have provided an opportunity to test the analysis techniques and instrumentation, they have not provided an adequate combination of spatial resolution, energy resolution, and aperture to perform true quantitative global imaging of the aurora. The full potential of x-ray imaging demands instrumentation based at high altitude in order to view the entire polar region. The system must also be capable of providing adequate measurements of x-ray spectra on reasonable time scales and Figure A.2 shows the integration time needed to produce a quantitative x-ray image as a function of altitude and spatial resolution within the aurora; here an aperture of 100 cm2 Is assumed. The ISTP polar spacecraft will carry multispectral auroral imagers that will cover visible, ultraviolet, and x-ray wavelengths, and the payload will also include advanced instrumentation for measurements of local plasma physics phenomena.

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66 DMSP, NOAA, SHUTTLE TIROS 1000 A - O 100 - o Oh LL A: ~ 10 oh 1 GEOSYNCHRONOUS LUNAR MOLNIYA ORBIT ,c,G /~ oils - '//? 1 00 1 000 10K ALTITUDE (km) 100K 1M FIGURE A.2 Temporal and spatial resolution as a function of distance from source to x-ray detector. Required integration time A = lOO cm2. A.3 PROSPECTS FOR EXTREME ULTRAVIOLET IMAGING OF PLASMA IN THE MAGNETOSPHERE Plasma temperatures above about 40,000K generally pro- duce ions with resonance transitions into the EUV region of the spectrum. In this temperature regime, energy lost by racliative processes is then dominantly in the EUV, and study of emissions at the short wavelengths can yield accurate diagnostic Formation about the plasma. An example of EUV plasma imaging involves the data provided by the Voyager spectrograph as it detected the plasma torus of Jupiter's moon, To. Successive sweeping of the field of view of this one-dimensional imaging system has yielded the three-dimensional image of the jovian system shown in Figure

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67 INTERSTELLAR WIND H Ly ~ so ~ on INTERSTELLAR WIND He 5" A AURORAL H. BANDS . ., ~~A ~ ,' PLANETARY H Low >a lV- rev ..rA\J~ ~,f,f~ (A -C~05 FIGURE A.3 Spatially and spectrally resolved image of Jupiter and the lo plasma torus obtained by the Voyager EUV spectrometer. A.3. These observations have provided many pictorial views of the integrated emission from the plasma torus. The measurement of the characteristics of the EUV source (size, shape, spectral in- tensity, etc.) allows the identification of the ion species, and the deterniination of the number density and electron temperature distributions. On the basis of these points of reference we can make a reason- able deterniination of our ability to image the terrestrial magneto- sphere with EUV radiation. It is currently technically feasible to measure emission brightness at the level of 0.01 Rayleigh, within a reasonable tune frame of about 100 s. On this basis an im- age of Earth's magnetosphere in the resonance fluorescence of the He+ 304 ~ line, for example, would provide an isophote map to a distance of 10 Re geocentric. Arguments at a sunilar level can be made for the detection of other species in emissions produced by collisions and by fluorescence. The workshop participants con- clude that the mapping of the plasmasphere and magnetosphere in EUV emission is an obtainable goal.

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68 Plasmaspheric and Magnetospheric Boundaries The dominant ion in the plasmasphere capable of producing EUV emission is He+. As noted above, the principal emission feature of this species is at 304 A, and this is produced primarily by resonance fluorescence of the solar line. Knowledge of the solar differential flux distribution and the spectral shape of the scattered radiation allows diagnostics of bulk motion of the plasma as well as plasma temperatures. The image of the terrestrial plasmasphere obtained by a photometer coupled to an array detector is illus- trated in Figure A.4; these profiles have been calculated using a specific mode! of the He+ distribution derived from Dynamics Ex- plorer observations, as shown in Figure A.5. The ability to measure EUV emission at the level of 0.01 Rayleigh in an imaging system is entirely possible In the near future. Recent AMPT~CCE ob- servations of Hey suggest that the magnetopause boundary could also be imaged. Moreover, it ~ known that the distant plasma sheet is populated by Hey (and O+) during storms, and hence imaging of dynamical tail phenomena during substorms should also be possible. Other less extensive species having lower abundances, such as 0, 0+, N. and N+, could be observed with an imaging spectrome- ter and would provide measurement of the nature of the interface between the magnetosphere and the ionosphere. In general, these species are excited by both plasma electrons and fluorescence of solar lines. Spectral analysis of the emissions from these species are diagnostic of basic plasma properties; composition, density, and temperature of both ions and electrons. The analysis technique has been used in astrophysics for many years (for instance, in the study of gaseous nebula), and it is equally suited to the study of the plasma environments of Venus, the outer planets, and comets, provided that suitable atom and molecular transitions are chosen for each particular system. A col- umn abundance of 10~/cm2 of Oll ions interacting with electrons having typical auroral energies could be detected by present-day instrument design with a 100~8 integration time, for example. Given somewhat larger integration times, processes at the bow shock and magnetosheath should be observable. Bulk motions in the magnetotai} may be traced through successive measurements of structural features and through high-resolution spectral line shape measurements.

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69 / 0.~- -in :~N 0;1 0 \ 1 ~40~_~ ~ > \ FIGURE A.4 He+ 304 ~ isophote~ for distribution model 1 (see Figure A.5), as seen from two views: (top) a point on the Earth-Sun line in the plane of the magnetic equator, and (bottom) a point on the noon meridian at a magnetic latitude of 35. These global observations of the magnetosphere must clearly be linked to direct parallel measurements of solar activity, and followed through a time scale of one or more major solar cycles.

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70 3.0 + 1: 2 . 0 Cal o 1.0 0.0 _ .''''' "am\ ~  ~ ~ Model ~ ~ a. \Model I . . . . . . . 1 2 3 4 5 6 7 8 9 L SHELL FIGURE A.5 Model He+ distributions derived from Dynamics Explorer observations. Locations for Observing Stations Earth's magnetosphere can be unaged from a range that allows the whole system to be continuously ~ the field of view of the imager. This can be done from the I.1 I,agr~gian point, as a control monitor, with spacecraft at the L4 and L5 Lagrangian points or an instrument on a lunar base to provide stereoscopic capability. The Moon and the L4 and L5 points have many good features as sites for these measurements. The L4 and L5 points are at lunar distance, preceding and following the Moon at 60 to the Earth- Moon line. The 120 aspect angle is almost ideal for stereoscopic studies of discrete plasma motions of detached plasmas. The lunar orbital rate is slow enough to aDow correlated studies over several days. The time scale is also about right for the study of typical solar-magnetospheric interactions. The changing aspect of the lunar orbit is important for viewing interface regions such as the

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71 magnetopause and bow shock surfaces. These interfaces need to be investigated with long optical paths that occur when the viewing direction is nearly tangent to the surface. For instance, the bow shock should be viewed tangentially over an arc-shaped region of the sky. The tangent line progresses so as to result in a comnIete survey of the complete bow shock in each lunar period. Simultaneous imaging of the magnetospheric system from the L1 point is also required. This ~ an important viewing station because whereas L4, L5, and the Moon orbit the Earth, the L1 view is stable and stationary with respect to the Sun's direction. The solar wind can also be measured continuously from the L1 station, allowing detailed study of the effect of solar wind variability on the magnetospheric system. From here one could also study changes in the solar flux spectrum and intensity; this information is of importance for atmospheric analysis, and it is also needed for the complete interpretation of the resonance emissions from the magnetospheric plasma. ~ . [id" Lasers can be used to excite emissions from the constituents of the ionospheric and magnetospheric plasma, as well as the at- mosphere. This lidar technique involves the excitation of ions and atoms by a light source with highly controlled characteristics, and this, in turn, leads to precise Formation on species concentra- tion, location, and velocities. NASA ~ developing such a lidar system for remote sensing of the rniddIe atmosphere from the Space Shuttle and Space Station, with planned operations in the 1990~. Although the densities of magnetospheric particles are very low in comparison with atmospheric densities, the path lengths are long, and therefore acceptable signals may be generated. The ma- jor obstacle to applying this technique to magnetospheric remote sensing is the lack of a laser with reasonable efficiencies to oper- ate at ultraviolet wavelengths. However, DOD requirements could lead to development of an ultraviolet laser, and NASA should be prepared to take advantage of such advances and utilize laser technology for remote mapping of the magnetospheric plasma.

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72 A.4 PROSPECTS FOR NEUTRAL PARTICLE DIALING OF PLANETARY MAGNETOSPHERES Background A new window into magnetospheric physics has been opened with the detection of energetic neutral particles (50 keV) emanat- ing from the magnetospheres of Earth, Jupiter, and Saturn. These measurements directly point the way toward an innovative class of instruments devoted to global imaging of magnetospheric neu- tral particle emissions. Energetic neutrals are created within the magnetosphere by charge exchange reactions between fast magne- tospheric ions and ambient neutral atoms or molecules (see Figure Am. Since the resulting fast neutrals escape from the magneto- sphere on rectilinear trajectories, they can be used to image the neutral-particle-emitting regions of the magnetosphere. The re- sulting images provide the only known means for remote sensing on a global scale of the magnetospheric energetic charged particle populations. In this way energetic neutral images are complementary to ul- traviolet and optical images of the magnetosphere, which remotely sense only the low-energy (~5 keV) charged particle populations. Unlike conventional spacecraft observations of charged particles that are essentially single-point measurements that sample only very small regions at any time, energetic neutral particles can im- age the entire complex magnetospheric system at a single instant. Charged particle measurements sample only a region comparable to the mean free path if scattering occurs; otherwise they sample only a flux tube of radius comparable to the gyroradius. Both length scales are much smaller than global length scales. Some very low frequency plasma waves are observed after propagation from global distances, but these are of such long wavelength that little or no directional information can be obtained. Expected Results Global imaging of neutral particle emissions from Earth's mag- netosphere will yield a completely new global view of dynamic processes such as changes in plasma sheet configuration, growth and decay of the ring current, and auroral zone charged parti- cle precipitation. Imaging studies of the interrelationships among

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73 IMAGING NEUTRAL PARTICLE DETECTOR ATOM ~ ~ CHARGE EXCHANGE (7= r ION FIGURE A.6 Energetic neutral particle imaging of the fast ion and ambient neutral population. An energetic trapped ion captures an electron from an ambient neutral in a charge exchange reaction, becoming an energetic neutral atom, which then escapes the magnetosphere to the detector along a direction determined by the ion's velocity at the time of the reaction. these processes on a global scale should resolve the long-standing debates concerning the nature of geomagnetic substorms. Coarse global images of Earth's ring current using neutral particle emissions have already been obtained. Analysis of ISE~1 and IMP 7,8 data has revealed energetic neutral particle emissions from charge exchanges between ring current ions and hydrogen atoms of Earth's geocorona. Figure A.7 is an example (constructed from an eigh~pixe! ISE~1 image near the midnight meridian at 20 Re) of the energetic neutral particle emission during the recovery phase of a magnetic storm; the emission comes from the magnetic equatorial region of the ring current (3 S ~ < 5), and it is strongly asymmetrical, being concentrated in the dusk-m~dnight section.

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74 Sun April 18, 1978 / \ ( 7th ) ~ O Spin 21 sector 6 Cad Magnetic pole {04 UT) \ / - :: . - .,\ :: ; . . .\ ,., - wq I jam FIGURE A.7 Energetic neutral particle emission pattern during the re- covery of a geomagnetic storm ISEE-1 near the midnight meridian at 20 Re. Ranking of the pixel intensity (in lozenges marking the center of each pixel) indicates the greatest intensity from the late evening quadrant of the magnetic equatorial region (3 < L ~ 5~. Figure A.8 shows how a high-resolution neutral imager could provide much more information. The top pane} contains the "im- age~ expected from an ideal energetic neutral atom detector lo- cated at X-8Re, Y = 0, Z = 5Re. For simplicity a dipole magnetic field, a nearly isotropic equatorial pitch angle d~tribu- tion with empty loss cone, and an azimuthally symmetric ring current are assumed. The bottom pane! of Figure A.S then shows the line-of-sight ion flux column density for the main phase ring current distribution deduced from the measured neutral atom in- tensity profile in the bottom panel. Energetic neutral particles also contain specific information on the composition of the magnetospheric energetic ions. For example, from Table A.! the decay time and the energy spectrum of the neutral particle emissions observed during the recovery phase of a small magnetic storm are given; here it was deduced that O+ was a significant component of the ring current. Thm illustrates the strong need for composition resolution capability in this new class of instruments.

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75 _CR~ - _ ~~ 1 ~ ~ o US ._ ~ I so m o _ ~ - o ._ Co' ~ ., ._ o A, ~ ._ o 3 o Ce Cal b,O Al ~ ._ ~ L. so oo ~ lo. 4. L. oo Cot P4 = Cot X d :^ 1~ moo ._ go. ~ ~ ~ ~ X _ ~ ~ a _I Go ~ {i] at,' 08 O ~ O =_'

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76 TABLE A.1 Nominal Neutral Particle Intensities from Various Components of Earth's Magnetosphere E ~ 40 keV Proton Hydrogen Energetic Neural Count Rate per Intensity Column Density Intensity1 (cm ~ Pixel, Angular (cm Her (cm ) so keV) Resolution keV)~ Near-Earth 104 lolo 0.01 0.1/sec,-10 Plasma Sheet Quiet Time 2 x 104 5 x 1011 1a O.s/~,a -2O Radiation Belh Storm Time 3x 105 5 x 1011 1Sa 7.5/s,a -2O Ring Current aEnergetic neutral intensities and count rates up to an order of magnitude greater are predicted if O dominates rather than protons. The neutral particle intensity from charge exchanges in the Earths magnetosphere is estimated from the integral along the line of sight of the product of the ion intensity, the charge exchange cross section, and the neutral density. Table A.! gives nominal estimates of neutral particle intensities at E ~ 40 keV from the near-Earth plasma sheet, the quiet time radiation belts, and the storm time ring current. The first of these refers to an equatorial line of sight near 10 Re through the plasma sheet. Both quiet time radiation belt and storm time ring current refer to lines of sight near ~4. A 2~keV energy band is assumed, and a charge exchange cross section equal to 10-~6 cmi2 (appropriate for 5~ keV protons incident on hydrogen) is used. The charge exchange cross section and predicted neutral intensities are about 10 tunes greater if O+ ions are assumed to dominate protons, since the charge exchange crow section is 10-~5 cm2 for ~100 keV OF ions near incident on hydrogen. Nominal count rates per pixel are shown in Table A.~. These rates apply to pixel whose fields of view are filled by the respec- tive emitting regions. This new class of instruments will be able to image the quiet tune radiation belts and the storm tune rug cur- rent with high angular resolution (2) and high time resolution (13 to 200 s). They also unage the near-Earth plasma sheet at lower resolution. These studies will revolutionize our understanding of global dynamic processes such as magnetic substorms, because we will, for the first time, be able to see the entire magnetosphere in one image. Energetic neutral particle imaging can revolutionize

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77 our understanding of planetary magnetospheres In general. The Voyager spacecraft detected energetic charge exchange neutrals from both Jupiter and Saturn, but the instruments could not pro- duce images. At Jupiter, energetic neutral imaging fulfills a unique role. It is the only known way of continuously sampling the very intense charged particle population in the innermost region of the Jovian radiation belts, where particle detectors are saturated (and heavily damaged) by the penetrating radiation. We still do not know if there are magnetic storms at Jupiter and Saturn (or Uranus) similar to those at Earth. Global anages of their ener- getic ion populations offer the means to answer this question and perhaps to discover a new generalization of the concept of mag- netic store=. Remote sensing, particularly from a high-~nclination orbit, could be compared directly with earth-based optical and ultraviolet torus images and radio observations of synchrotron radiation. A.5 CONCLUSIONS AND RECOMMENDATIONS The exploration of the Earth's environment has been highly incomplete in the sense that we have not yet developed the tech- nology to determine the complete dependence of atmospheric and magnetospheric dynamics on solar activity. Our understanding of the behavior of the Sun's emissions over a solar cycle ~ rudi- mentary, and our knowledge of the global response of the Earth's magnetosphere on both a short- and a long-term basis ~ very incomplete. The workshop participants have investigated the future needs of the discipline and conclude that the full ISTP program will provide an excellent data base for the development of one or more dynamic global models of the Earth's magnetosphere. They aLso conclude that in the post-ISTP era, a new approach will be needed to ensure that the correct mode} is adopted, and to verify its accuracy. The workshop discussions strongly suggest that the only prac- tical post-ISTP approach to testing of global magnetospheric mod- els Is one that utilizes techniques to provide global images of the magnetosphere. Fortunately, the workshop deliberations also sug- gest that this imaging concept ~ a realistic one. It was demon- strafed (using Voyager data from Jupiter) that atomic lines are excited by ambient electrons with sufficient intensity to provide

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78 images of coo} dense plasma boundaries. For Earth the Hey 304 ~ line appears to be the best candidate for unaging the plasma- sphere, the bow shock and magnetopause region, and (during storm conditions) the plasma sheet in the geomagnetic tail; how- ever, this is currently a theoretical concept, since a terrestrial He+ 304 ~ imager has not been flown. The more energetic plasmas (ring current, auroral region, and so on) are best ~imaged" by searching for energetic neutral atoms produced by charge exchange. The very low resolution results already obtained with the ISE~1 energetic particle analyzer verify the concept and show the power of this technique, but they also point to the need for development of instruments with higher resolution. The workshop participants urge NASA to support the devel- opment and testing of suitable sensitive high-resolution magneto- spheric imaging instruments with the aim of establishing a full- fledged magnetospheric imaging my - ion in the post-ISTP time frame.