Comparing and contrasting dispersionless injections at geosynchronous orbit during a substorm event

TitleComparing and contrasting dispersionless injections at geosynchronous orbit during a substorm event
Publication TypeJournal Article
Year of Publication2017
AuthorsKronberg, EA, Grigorenko, EE, Turner, DL, Daly, PW, Khotyaintsev, Y, Kozak, L
JournalJournal of Geophysical Research: Space Physics
Volume122
Start Page3055
Issue3
Date Published03/2017
KeywordsAcceleration; current wedge; Dipolarization; particle injections; substorm; ULF waves; Van Allen Probes
AbstractParticle injections in the magnetosphere transport electrons and ions from the magnetotail to the radiation belts. Here we consider generation mechanisms of “dispersionless” injections, namely, those with simultaneous increase of the particle flux over a wide energy range. In this study we take advantage of multisatellite observations which simultaneously monitor Earth's magnetospheric dynamics from the tail toward the radiation belts during a substorm event. Dispersionless injections are associated with instabilities in the plasma sheet during the growth phase of the substorm, with a dipolarization front at the onset and with magnetic flux pileup during the expansion phase. They show different spatial spread and propagation characteristics. Injection associated with the dipolarization front is the most penetrating. At geosynchronous orbit (6.6 RE), the electron distributions do not have a classic power law fit but instead a bump on tail centered on ∼120 keV during dispersionless electron injections. However, electron distributions of injections associated with magnetic flux pileup in the magnetotail (13 RE) do not show such a signature. We surmise that an additional resonant acceleration occurs in between these locations. We relate the acceleration mechanism to the electron drift resonance with ultralow frequency waves localized in the inner magnetosphere.
URLhttp://onlinelibrary.wiley.com/doi/10.1002/2016JA023551/full
DOI10.1002/2016JA023551
Short TitleJ. Geophys. Res. Space Physics


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