%AMotoba, T. [The Johns Hopkins University Applied Physics Laboratory Laurel MD USA]%AOhtani, S. [The Johns Hopkins University Applied Physics Laboratory Laurel MD USA]%AClaudepierre, S. [Space Sciences Department Aerospace Corporation Los Angeles CA USA, Department of Atmospheric and Oceanic Sciences University of California Los Angeles CA USA]%AReeves, G. [Los Alamos National Laboratory Los Alamos NM USA]%AUkhorskiy, A. [The Johns Hopkins University Applied Physics Laboratory Laurel MD USA]%ALanzerotti, L. [Center for Solar‐Terrestrial Research New Jersey Institute of Technology Newark NJ USA]%BJournal Name: Journal of Geophysical Research: Space Physics; Journal Volume: 125; Journal Issue: 9; Related Information: CHORUS Timestamp: 2023-08-29 16:09:47 %D2020%IDOI PREFIX: 10.1029 %JJournal Name: Journal of Geophysical Research: Space Physics; Journal Volume: 125; Journal Issue: 9; Related Information: CHORUS Timestamp: 2023-08-29 16:09:47 %K %MOSTI ID: 10374658 %PMedium: X %TDynamic Properties of Particle Injections Inside Geosynchronous Orbit: A Multisatellite Case Study %XAbstract

Four closely located satellites at and inside geosynchronous orbit (GEO) provided a great opportunity to study the dynamical evolution and spatial scale of premidnight energetic particle injections inside GEO during a moderate substorm on 23 December 2016. Just following the substorm onset, the four spacecraft, a LANL satellite at GEO, the two Van Allen Probes (also called “RBSP”) at ~5.8RE, and a THEMIS satellite at ~5.3RE, observed substorm‐related particle injections and local dipolarizations near the central meridian (~22 MLT) of a wedge‐like current system. The large‐scale evolution of the electron and ion (H, He, and O) injections was almost identical at the two RBSP spacecraft with ~0.5REapart. However, the initial short‐timescale particle injections exhibited a striking difference between RBSP‐A and ‐B: RBSP‐B observed an energy dispersionless injection which occurred concurrently with a transient, strong dipolarization front (DF) with a peak‐to‐peak amplitude of ~25 nT over ~25 s; RBSP‐A measured a dispersed/weaker injection with no corresponding DF. The spatiotemporally localized DF was accompanied by an impulsive, westward electric field (~20 mV m−1). The fast, impulsiveE × Bdrift caused the radial transport of the electron and ion injection regions from GEO to ~5.8RE. The penetrating DF fields significantly altered the rapid energy‐ and pitch angle‐dependent flux changes of the electrons and the H and He ions inside GEO. Such flux distributions could reflect the transient DF‐related particle acceleration and/or transport processes occurring inside GEO. In contrast, O ions were little affected by the DF fields.

%0Journal Article