Propagation of EMIC Waves Inside the Plasmasphere: A Two-Event Study

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Abstract
Electromagnetic ion cyclotron (EMIC) waves are important for the loss of high-energy electrons in the radiation belt. Based on the measurements of Van Allen Probes, two events during the same storm period are presented to study the propagation of EMIC waves. In the first event, left-handed polarized EMIC waves were observed near the plasmapause, while right-handed waves were observed in the inner plasmasphere. The Poynting flux of the right-hand waves was mainly directed inward and equatorward, and no positive growth rates were obtained in the region of these right-hand waves, indicating the inward propagation of the waves from a higher L-shell. In the second event, the wave vectors were quasi-perpendicular to the background magnetic field inside the plasmaspheric plume but became quasi-parallel outside. This phenomenon can be explained by the refraction of the large density gradient, which qualitatively satisfies Snell\textquoterights law. These observations provide indirect evidence of the inward propagation of the EMIC waves and give a new insight on how density gradients may modify wave properties
Year of Publication
2019
Journal
Journal of Geophysical Research: Space Physics
Date Published
10/2019
ISSN Number
2169-9380
URL
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA027055
DOI
10.1029/2019JA027055
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