Energetic electron injections deep into the inner magnetosphere associated with substorm activity

Abstract

From a survey of the first nightside season of NASA's Van Allen Probes mission (December 2012 to September 2013), 47 energetic (tens to hundreds of keV) electron injection events were found at L shells ≤ 4, all of which are deeper than any previously reported substorm-related injections. Preliminary details from these events are presented, including how all occurred shortly after dipolarization signatures and injections were observed at higher L shells, how the deepest observed injection was at L ∼ 2.5, and, surprisingly, how L ≤ 4 injections are limited in energy to ≤250 keV. We present a detailed case study of one example event revealing that the injection of electrons down to L ∼ 3.5 was different from injections observed at higher L and likely resulted from electrons interacting with a fast magnetosonic wave in the Pi2 frequency range inside the plasmasphere. These observations demonstrate that injections occur at very low L shells and may play an important role for inner zone electrons.