Van Allen Probes observations of unusually low frequency whistler mode waves observed in association with moderate magnetic storms: Statistical study

TitleVan Allen Probes observations of unusually low frequency whistler mode waves observed in association with moderate magnetic storms: Statistical study
Publication TypeJournal Article
Year of Publication2015
AuthorsCattell, CA, Breneman, AW, Thaller, SA, Wygant, JR, Kletzing, CA, Kurth, WS
JournalGeophysical Research Letters
Volume42
Issue18
Pagination7273 - 7281
Date Published09/2015
KeywordsChorus; outer radiation belt; Van Allen Probes
AbstractWe show the first evidence for locally excited chorus at frequencies below 0.1 fce (electron cyclotron frequency) in the outer radiation belt. A statistical study of chorus during geomagnetic storms observed by the Van Allen Probes found that frequencies are often dramatically lower than expected. The frequency at peak power suddenly stops tracking the equatorial 0.5 fce and f/fce decreases rapidly, often to frequencies well below 0.1 fce (in situ and mapped to equator). These very low frequency waves are observed both when the satellites are close to the equatorial plane and at higher magnetic latitudes. Poynting flux is consistent with generation at the equator. Wave amplitudes can be up to 20 to 40 mV/m and 2 to 4 nT. We conclude that conditions during moderate to large storms can excite unusually low frequency chorus, which is resonant with more energetic electrons than typical chorus, with critical implications for understanding radiation belt evolution.
URLhttp://doi.wiley.com/10.1002/2015GL065565http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL065565
DOI10.1002/2015GL065565
Short TitleGeophys. Res. Lett.


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