Variation in crossover frequency of EMIC waves in plasmasphere estimated from ion cyclotron whistler waves observed by Van Allen Probe A

TitleVariation in crossover frequency of EMIC waves in plasmasphere estimated from ion cyclotron whistler waves observed by Van Allen Probe A
Publication TypeJournal Article
Year of Publication2016
AuthorsMatsuda, S, Kasahara, Y, Kletzing, CA
JournalGeophysical Research Letters
Volume43
Issue1
Pagination28 - 34
Date Published01/2016
KeywordsEMIC wave; ion cyclotron whistler; plasmasphere, heavy ions; Van Allen Probes
AbstractWe report variations in the propagation of the H+ band ion cyclotron whistlers observed by Van Allen Probe A. Ion cyclotron whistlers are one of the EMIC (electromagnetic ion cyclotron) waves generated by mode conversion from lightning whistlers. Crossover frequency is an important frequency for the ion cyclotron whistlers, which is a function of the variations in the local heavy-ion composition. We surveyed waveform data obtained by the Electric and Magnetic Field Instrument and Integrated Science instrument and found that 3461 H+ band ion cyclotron whistlers were observed from 572 km to 5992 km in altitude. The main finding is that the crossover frequencies of the observed events decreased with increasing altitude. These results support the hypothesis that the total heavy-ion density decreases with increasing altitude. Furthermore, in 96% of all observed events, the crossover frequencies exceeded inline image, which suggests that the EMIC dispersion relation contains a frequency gap of around inline image.
URLhttp://doi.wiley.com/10.1002/2015GL066893
DOI10.1002/2015GL066893
Short TitleGeophys. Res. Lett.


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