title: Spacecraft surface charging within geosynchronous orbit observed by the Van Allen Probes.
abstract: Using the Helium Oxygen Proton Electron (HOPE) and Electric Field and Waves (EFW) instruments from the Van Allen Probes, we explored the relationship between electron energy fluxes in the eV and keV ranges and spacecraft surface charging. We present statistical results on spacecraft charging within geosynchronous orbit by L and MLT. An algorithm to extract the H+charging line in the HOPE instrument data was developed to better explore intense charging events. Also, this study explored how spacecraft potential relates to electron number density, electron pressure, electron temperature, thermal electron current, and low-energy ion density between 1 and 210 eV. It is demonstrated that it is imperative to use both EFW potential measurements and the HOPE instrument ion charging line for examining times of extreme spacecraft charging of the Van Allen Probes. The results of this study show that elevated electron energy fluxes and high-electron pressures are present during times of spacecraft charging but these same conditions may also occur during noncharging times. We also show noneclipse significant negative charging events on the Van Allen Probes.
authors.affiliation: Department of Climate and Space Engineering University of Michigan Ann Arbor Michigan USA.
authors.forename: Lois K
authors.initials: LK
authors.lastname: Sarno-Smith
authors.affiliation: Los Alamos National Laboratory Los Alamos New Mexico USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Larsen
authors.affiliation: Los Alamos National Laboratory Los Alamos New Mexico USA.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Skoug
authors.affiliation: Department of Climate and Space Engineering University of Michigan Ann Arbor Michigan USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Liemohn
authors.affiliation: School of Physics and Astronomy University of Minnesota Minneapolis Minnesota USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Breneman
authors.affiliation: School of Physics and Astronomy University of Minnesota Minneapolis Minnesota USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Wygant
authors.affiliation: Planetary Science Institute Tucson Arizona USA.
authors.forename: Michelle F
authors.initials: MF
authors.lastname: Thomsen
keywords: EFW; HOPE; Van Allen Probes; spacecraft charging; surface charging