Local time variations of high-energy plasmaspheric ion pitch angle distributions

TitleLocal time variations of high-energy plasmaspheric ion pitch angle distributions
Publication TypeJournal Article
Year of Publication2016
AuthorsSarno-Smith, LK, Liemohn, MW, Skoug, RM, Larsen, BA, Moldwin, MB, Katus, RM, Wygant, JR
JournalJournal of Geophysical Research: Space Physics
Date Published07/2016
Keywordsalgorithm; Magnetosphere; pitch angles; plasmasphere; spacecraft potential corrections; Van Allen Probes
AbstractRecent observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument revealed a persistent depletion in the 1–10 eV ion population in the postmidnight sector during quiet times in the 2 < L < 3 region. This study explores the source of this ion depletion by developing an algorithm to classify 26 months of pitch angle distributions measured by the HOPE instrument. We correct the HOPE low energy fluxes for spacecraft potential using measurements from the Electric Field and Waves (EFW) instrument. A high percentage of low count pitch angle distributions is found in the postmidnight sector coupled with a low percentage of ion distributions peaked perpendicular to the field line. A peak in loss cone distributions in the dusk sector is also observed. These results characterize the nature of the dearth of the near 90° pitch angle 1–10 eV ion population in the near-Earth postmidnight sector. This study also shows, for the first time, low-energy HOPE differential number fluxes corrected for spacecraft potential and 1–10 eV H+ fluxes at different levels of geomagnetic activity.
URLhttp://doi.wiley.com/10.1002/2015JA022301
DOI10.1002/2015JA022301
Short TitleJ. Geophys. Res. Space Physics


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