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 les...

Full description

Saved in:
Bibliographic Details
Published in:Journal of geophysical research. Space physics 2015-03, Vol.120 (3), p.1646-1660
Main Authors: Sarno‐Smith, Lois K., Liemohn, Michael W., Katus, Roxanne M., Skoug, Ruth M., Larsen, Brian A., Thomsen, Michelle F., Wygant, John R., Moldwin, Mark B.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Charge exchange
Density
Depletion
Diurnal variations
Electric fields
Electric potential
Energy
Geophysics
Helium
ion composition
Ionosphere
KP index
Measuring instruments
Plasma physics
Plasmasphere
postmidnight
Probes
quiet time magnetosphere
Space probes
Spacecraft
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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 and 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 postmidnight sector (1–4 magnetic local time), followed by O+ and then He+. The relative depletion of each species across the postmidnight 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 instrument spacecraft potential to rule out spacecraft charging. Our conclusion is that the postmidnight ion disappearance is due to diurnal ionospheric temperature variation and charge exchange processes. Key Points One to ten eV ion depletion in quiet time postmidnight sector Depletion varies by ion species not ordered by mass Strong diurnal variation in high‐energy tail of plasmasphere
ISSN:2169-9380
2169-9402
DOI:10.1002/2014JA020682