Dynamic Properties of Particle Injections Inside Geosynchronous Orbit: A Multisatellite Case Study

Area of Science:

• Space Physics
• Magnetospheric Physics
• Substorm Dynamics

Background:

• Geosynchronous orbit (GEO) is crucial for understanding space weather.
• Energetic particle injections during substorms are key phenomena.
• Satellite observations provide in-situ data on magnetospheric dynamics.

Purpose of the Study:

• Investigate the dynamical evolution and spatial scale of premidnight energetic particle injections inside GEO.
• Analyze the impact of substorm onset and dipolarization fronts on particle behavior.
• Differentiate particle injection characteristics and their relation to localized fields.

Main Methods:

• Utilized data from four closely located satellites (LANL, Van Allen Probes/RBSP, THEMIS).
• Analyzed in-situ measurements of energetic particles (electrons, H, He, O) and electromagnetic fields.
• Examined particle injection characteristics, dipolarization fronts (DF), and electric fields.

Main Results:

• Observed substorm-related particle injections and local dipolarizations near 22 MLT.
• Found identical large-scale electron and ion injections at two closely spaced RBSP spacecraft.
• RBSP-B observed energy dispersionless injection with a strong, transient dipolarization front (DF); RBSP-A observed a dispersed/weaker injection without a DF.
• Localized DF and westward electric field caused impulsive E × B drift, transporting particles from GEO to ~5.8 RE.
• DF fields significantly altered energy- and pitch angle-dependent electron and ion (H, He) flux changes within GEO.

Conclusions:

• Localized dipolarization fronts significantly impact energetic particle dynamics within geosynchronous orbit.
• The observed flux distributions suggest transient DF-related particle acceleration and/or transport processes.
• Oxygen ions appear less affected by the dipolarization front fields compared to other species.