Characteristics and Generation of Low-Frequency Magnetosonic Waves Below the Proton Gyrofrequency

Author
Keywords
Abstract
We report a Van Allen Probes observation of large-amplitude magnetosonic waves with the peak intensity below the proton gyrofrequency (fcp), which may potentially be misinterpreted as electromagnetic ion cyclotron waves. The frequency spacing of the wave harmonic structure suggests that these magnetosonic waves are excited at a distant source region and propagate radially inward. We also conduct a statistical analysis of low-frequency magnetosonic waves below fcp based on the Van Allen Probes data from October 2012 to December 2018. The spatial distribution shows that these low-frequency magnetosonic emissions are dominantly observed inside the plasmasphere from the prenoon to the midnight sector within 5\textdegree of the geomagnetic equator and typically have modest-to-strong wave amplitudes ranging from tens of pT to hundreds of pT. Our study provides insight into understanding the generation and propagation of these low-frequency magnetosonic waves in the Earth\textquoterights inner magnetosphere.
Year of Publication
2019
Journal
Geophysical Research Letters
Volume
46
Number of Pages
11652-11660
Date Published
10/2019
ISSN Number
0094-8276
URL
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL085372
DOI
10.1029/2019GL085372