Multi-point Observations and Modeling of Particle Injections During Substorms

Abstract:

Dispersionless and dispersed particle injections associated with substorms have been studied for many years based on observations acquired primarily at geosynchronous orbit. A general picture that has emerged is that particles are energized and rapidly transported/organized behind an "injection boundary" that penetrates closer to Earth in some magnetic local time sector (e.g. the so-called double-spiral injection boundary model). While this picture provides a very good description of injections at geosynchronous orbit, with the launch of the Van Allen Probes mission, we are now able to explore the evolution of injection signatures well inside of geosynchronous orbit at multiple locations as well. We find that the injection boundary model also appears to reproduce a number of complicated types of dispersion patterns observed in the Van Allen Probes particle data. The dispersion patterns are found to depend dramatically on orbital configuration and timing of onset relative to the phasing of the spacecraft in their orbits. In addition to observational results, we present results of simulated dispersion patterns obtained from the injection boundary model using guiding center particle tracing in two different field configurations: 1) a simplistic dipole magnetic field with Volland-Stern electric field, and 2) RAM/SCB running in the Space Weather Modeling Framework.