Electron butterfly distribution modulation by magnetosonic waves

Author
Keywords
Abstract
The butterfly pitch angle distribution is observed as a dip in an otherwise normal distribution of electrons centered about αeq=90\textdegree. During storm times, the formation of the butterfly distribution on the nightside magnetosphere has been attributed to L shell splitting combined with magnetopause shadowing and strong positive radial flux gradients. It has been shown that this distribution can be caused by combined chorus and magnetosonic wave scattering where the two waves work together but at different local times. Presented in our study is an event on 21 August 2013, using Van Allen Probe measurements, where a butterfly distribution formation is modulated by local magnetosonic coherent magnetosonic waves intensity. Transition from normal to butterfly distributions coincides with rising magnetosonic wave intensity while an opposite transition occurs when wave intensity diminishes. We propose that bounce resonance with waves is the underlying process responsible for such rapid modulation, which is confirmed by our test particle simulation.
Year of Publication
2016
Journal
Geophysical Research Letters
Date Published
04/2016
URL
http://doi.wiley.com/10.1002/2016GL068161http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2F2016GL068161http://api.wiley.com/onlinelibrary/chorus/v1/articles/10.1002\%2F2016GL068161
DOI
10.1002/2016GL068161