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Title: Postmidnight depletion of the high-energy tail of the quiet plasmasphere

The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures the high energy tail of the thermal plasmasphere allowing study of topside ionosphere and inner magnetosphere coupling. We statistically analyze a 22 month period of HOPE data, looking at quiet times with a Kp index of less than 3. We investigate the high energy range of the plasmasphere, which consists of ions at energies between 1-10 eV and contains approximately 5% of total plasmaspheric density. Both the fluxes and partial plasma densities over this energy range show H+ is depleted the most in the post-midnight sector (1-4 MLT), followed by O+ and then He+. The relative depletion of each species across the post-midnight sector is not ordered by mass, which reveals ionospheric influence. We compare our results with keV energy electron data from HOPE and the Van Allen Probes Electric Fields and Waves (EFW) instrument spacecraft potential to rule out spacecraft charging. Our conclusion is that the post-midnight ion disappearance is due to diurnal ionospheric temperature variation and charge exchange processes
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States). Department of Atmospheric, Oceanic, and Space Sciences
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Planetary Science Institute, Tucson, Arizona (United States)
  4. Univ. of Minnesota, Minneapolis, MN (United States). School of Physics and Astronomy
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 2169-9380; TRN: US1600642
Grant/Contract Number:
NWX11AO60G; NWX144AC02G; AGS-1102863; AC52-06NA25396
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 3; Journal ID: ISSN 2169-9380
American Geophysical Union
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
Country of Publication:
United States