First observation of rising-tone magnetosonic waves

Author
Keywords
Abstract
Magnetosonic (MS) waves are linearly polarized emissions confined near the magnetic equator with wave normal angle near 90\textdegree and frequency below the lower hybrid frequency. Such waves, also termed equatorial noise, were traditionally known to be \textquotedbllefttemporally continuous\textquotedblright in their time-frequency spectrogram. Here we show for the first time that MS waves actually have discrete wave elements with rising-tone features in their spectrogram. The frequency sweep rate of MS waves, ~1 Hz/s, is between that of chorus and electromagnetic ion cyclotron (EMIC) waves. For the two events we analyzed, MS waves occur outside the plasmapause and cannot penetrate into the plasmasphere; their power is smaller than that of chorus. We suggest that the rising-tone feature of MS waves is a consequence of nonlinear wave-particle interaction, as is the case with chorus and EMIC waves.
Year of Publication
2014
Journal
Geophysical Research Letters
Volume
41
Number of Pages
7419-7426
Date Published
11/2014
URL
http://doi.wiley.com/10.1002/grl.v41.21http://doi.wiley.com/10.1002/2014GL061867
DOI
10.1002/grl.v41.2110.1002/2014GL061867