Magnetosonic wave excitation by ion ring distributions in the Earth's inner magnetosphere

TitleMagnetosonic wave excitation by ion ring distributions in the Earth's inner magnetosphere
Publication TypeJournal Article
Year of Publication2014
AuthorsMa, Q, Li, W, Chen, L, Thorne, RM, Angelopoulos, V
JournalJournal of Geophysical Research: Space Physics
Volume119
Issue2
Pagination844 - 852
Date Published02/2014
Keywordsmagnetosonic waves; ring current; THEMIS observation; wave excitation
AbstractCombining Time History of Events and Macroscale Interaction during Substorms (THEMIS) wave and particle observations and a quantitative calculation of linear wave growth rate, we demonstrate that magnetosonic (MS) waves can be locally excited by ion ring distributions in the Earth's magnetosphere when the ion ring energy is comparable to the local Alfven energy. MS waves in association with ion ring distributions were observed by THEMIS A on 24 November 2010 in the afternoon sector, both outside the plasmapause where the wave spectrum varied with fLHR and inside the plasmapause where the wave frequency band remained nearly constant. Our plasma instability analysis in three different regions shows that higher and narrow frequency band MS waves are excited locally outside the plasmapause, and lower and broad frequency band MS waves are excited in the region where the density slightly increases. However, there is no evidence for wave excitation inside the plasmapause, and wave propagation from a distant source is needed to explain their existence. The simulation of the MS wave growth rate spectra during this event agrees reasonably well with the observed wave magnetic field power spectra. We also simulated a MS wave event on 19 October 2011 in the dusk sector and found that the ion ring distribution with an ion ring energy slightly higher than the local Alfven energy can excite the typical broad band MS waves outside the plasmapause.
URLhttp://doi.wiley.com/10.1002/2013JA019591
DOI10.1002/2013JA019591
Short TitleJ. Geophys. Res. Space Physics


Page Last Modified: November 3, 2014