Imprints of impulse-excited hydromagnetic waves on electrons in the Van Allen radiation belts

TitleImprints of impulse-excited hydromagnetic waves on electrons in the Van Allen radiation belts
Publication TypeJournal Article
Year of Publication2015
AuthorsZhou, X-Z, Wang, Z-H, Zong, Q-G, Claudepierre, SG, Mann, IR, Kivelson, MG, Angelopoulos, V, Hao, Y-X, Wang, Y-F, Pu, Z-Y
JournalGeophysical Research Letters
Pagination6199 - 6204
Date Published08/2015
Keywordsdrift resonance; Radiation belt; ULF waves; Van Allen Probes; wave growth; wave-particle interaction
AbstractUltralow frequency electromagnetic oscillations, interpreted as standing hydromagnetic waves in the magnetosphere, are a major energy source that accelerates electrons to relativistic energies in the Van Allen radiation belt. Electrons can rapidly gain energy from the waves when they resonate via a process called drift resonance, which is observationally characterized by energy-dependent phase differences between electron flux and electromagnetic oscillations. Such dependence has been recently observed and interpreted as spacecraft identifications of drift resonance electron acceleration. Here we show that in the initial wave cycles, the observed phase relationship differs from that characteristic of well-developed drift resonance. We further examine the differences and find that they are imprints of impulse-excited, coupled fast-Alfvén waves before they transform into more typical standing waves. Our identification of such imprints provides a new understanding of how energy couples in the inner magnetosphere, and a new diagnostic for the generation and growth of magnetospheric hydromagnetic pulsations.
Short TitleGeophys. Res. Lett.

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