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Solar Wind-Magnetosphere Interactions via Low Energy Neutral Atom Imaging

Solar Wind-Magnetosphere Interactions via Low Energy Neutral Atom Imaging. T E Moore[1], M R Collier[1], M-C Fok[1], S A Fuselier[2], D. G. Simpson[1], G. R. Wilson[3], M. O. Chandler[4] 1. NASA’s Goddard Space Flight Center, Interplanetary Physics Branch, Code 692, Greenbelt, MD 20771

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Solar Wind-Magnetosphere Interactions via Low Energy Neutral Atom Imaging

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  1. Solar Wind-Magnetosphere Interactionsvia Low Energy Neutral Atom Imaging • T E Moore[1], M R Collier[1], M-C Fok[1], S A Fuselier[2], D. G. Simpson[1], G. R. Wilson[3], M. O. Chandler[4] • 1. NASA’s Goddard Space Flight Center, Interplanetary Physics Branch, Code 692, Greenbelt, MD 20771 • 2. Lockheed Martin Advanced Technology Center, Dept. H1-11, Bldg. 255, Palo Alto, CA 94304 • 3. Mission Research Corporation, 589 W. Hollis St., Suite 201, Nashua, NH 03062 • 4. National Space Science and Technology Center, NASA MSFC SD50, Huntsville AL 35805 • LENA was motivated by need for time-resolved ionospheric outflow observations. • Also responds to neutral atoms with energies up to a few keV (from sputtering). • As a result, we have been able to: • Show that ionospheric outflow responds to solar wind dynamic pressure variations. • Observe that the response is prompt. • Infer a heating source below 1000 km altitude for the larger flux events. • Use neutral atom emissions to reveal the magnetosheath, with cusp-related structures. • Infer dayside structure in the geocorona. . • Measured the annual variation of the neutral solar wind. • Probe the interstellar gas and dust in the inner solar system. • Directly observe the interstellar neutral atom focusing cone at 1 AU. • LENA imaging has thus proven to be a promising new tool for studying the interplanetary medium and its interaction with the magnetosphere, even from inside the magnetosphere. T E Moore - SW Interactions via LENA

  2. Low Energy Neutral Atoms (LENA) CME/Storm Onset and Response Hr Before Hr After Snap Perigee • Solar Wind LENA increase marks CME arrival at 0915 hrs. • Earth sector LENA respond within travel time of 35eV O0. T E Moore - SW Interactions via LENA

  3. Comparison with Ion Outflows LENA H/O/Total Images TIDE Polar Ion Outflows Neutral Fraction vs Source Altitude • Preliminary comparisons: • Some spatial correspondence (day - night here) • Flux comparison indicates low altitude source region • Best correspondence w/ auroral oval from transverse views (not shown) • Posters AGUsm01: SM72A-14 (Coffey et al.), -15(Wilson et al.) T E Moore - SW Interactions via LENA

  4. Simulated LENA Emissions Auroral zone emissions Uniform polar emissions T E Moore - SW Interactions via LENA

  5. Sources of Indirect SW-LENA Collier et al. Nov JGR p.24,893 T E Moore - SW Interactions via LENA

  6. Solar LENA flux profile Strong similarity to ram pressure profile observed at WIND. Tracking observed at some time scales, not others. T E Moore - SW Interactions via LENA

  7. Simulation of Indirect LENAs • Simulations performed by M.-C. Fok using MHD magnetosheath. • Analogous to ring current ENA simulations, using an CCMC (BatsRUS) MHD model of the magnetosheath, and looking out. • LOS integration from 8 to 50 RE, excepting antisunward 90° cone. Images collapsed in polar angle, for IMAGE. • No true solar LENAs assumed to arrive in solar wind here. 200 eV 4000 eV Dawn-Dusk Orbit Dawn-Dusk Orbit Noon-Midnight Orbit Noon-Midnight Orbit T E Moore - SW Interactions via LENA

  8. Solar wind flux or dynamic pressure increases produce a big reaction in LENA. • A brightening is seen especially between the sun pulse and the Earth (white line here). • Is this the expected relation between solar wind intensity and ENA emission from this region? T E Moore - SW Interactions via LENA

  9. We expect a very strong dependence because so many factors are affected by solar wind flux (and Pd). T E Moore - SW Interactions via LENA

  10. Simulation of Magnetosheath CE • CCMC Simulations based on BatsRUS Code • LOS integration from IMAGE spacecraft by M-C Fok. • Consider periods of enhanced Pd solar wind for compressed magnetopause. • Remote sensing of cusp and cleft possible with sufficient sensitivity and-or Pd. T E Moore - SW Interactions via LENA

  11. T E Moore - SW Interactions via LENA

  12. LENA spin modulation near the peak of the 31 March 2001 event at about 0450UT: CCMC (BatsRUS) MHD simulation of the 31 March 2001 event, showing magnetosheath density distribution along LENA lines of sight at about 0450 UT Seeing Magnetosheath Structure T E Moore - SW Interactions via LENA

  13. Remote-Sensing the Magnetosheath Simulations indicate features of the magnetosheath should be visible and are visible from inside the magnetosphere. Sun MS T E Moore - SW Interactions via LENA

  14. Evidence for Geocoronal Erosion? Data: LENA background adjusted flux > 30 eV Deflectors 5-50 RE 5-12 RE T E Moore - SW Interactions via LENA

  15. Short term, storm variations reflect solar wind intensity variations, CMEs, and distribution of the geocorona. Long term, seasonal variations reflect solar system distribution of neutral gas (interstellar and other sources) T E Moore - SW Interactions via LENA

  16. SW ENA Model of Bzowski et al.Icarus 1996 T E Moore - SW Interactions via LENA

  17. Limit on Inner Solar System Dust Collier et al., AGU SM2001 T E Moore - SW Interactions via LENA

  18. Predicted Direct ISN Observations Fuselier, 1997 T E Moore - SW Interactions via LENA

  19. Direct ISNs, Interpreted? T E Moore - SW Interactions via LENA

  20. 3D Interstellar Neutral Trajectories T E Moore - SW Interactions via LENA

  21. ISN Flux 12/1 1/1 2/1 3/1 12/1 2/1 1/1 3/1 T E Moore - SW Interactions via LENA

  22. Conclusions • We have been able to: • Validate earlier statistical inferences that ionospheric heating responds to solar wind dynamic pressure variations. • Observe that the response is prompt, as fast as hydromagnetic wave propagation speeds. • Infer that the heating source must lie lower than 1000 km altitude for the larger flux events. • Use neutral atom emissions to reveal the magnetosheath, with cusp-related structures. • Infer dayside structure in the geocorona, owing to solar wind erosion by charge exchange. • Measure the annual variation of the neutral solar wind. • Interpret annual variation in terms of interstellar neutral gas and dust in the inner solar system. • Directly observe the interstellar neutral atom focusing cone at 1 AU. T E Moore - SW Interactions via LENA

  23. Comparison with Dayside Aurora 8 June 2000 CME Arrival • See Fuselier et al., GRL 15 March 2001. • Before/After images of dayside aurora. • IMF Bz generally Northward. • Similar in many ways to 24 Sept 98 CME, with resultant Ionospheric Mass Ejection [Moore et al., GRL, 1999] T E Moore - SW Interactions via LENA

  24. Direct ISNs, Observed T E Moore - SW Interactions via LENA

  25. T E Moore - SW Interactions via LENA

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