Correlated Observation on Global Distributions of Magnetosonic Waves and Proton Rings in the Radiation Belts

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Abstract
Fast magnetosonic (MS) waves are excited by the ring distribution of energetic protons preferably when the ring velocity (VR) is within a factor of 2 above or below the local Alfvén speed (VA). Here we examine the global distributions of MS waves and proton rings with 0.5VA ≤ VR ≤ 2VA based on 64 months (from October 25, 2012 to February 28, 2018) of Van Allen Probes observations. The statistical results show that MS waves are present over a broad region of L = 1.2–6.0 and 00–24 magnetic local time (MLT), with a higher occurrence rate at L = 2.5–5.5 on the dayside. Proton rings occur mainly on the dayside of L > 5.0. During active geomagnetic periods, both MS waves and proton rings occur more frequently and extend to low L-shells. The current results provide the further observational evidence that MS waves can be excited by proton rings at a distant region and propagate to low L-shells.
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Year of Publication
2020
Journal
Journal of Geophysical Research: Space Physics
Volume
126
Number
Number of Pages
e2020JA028354
Date Published
12/2020
URL
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JA028354
DOI
https://doi.org/10.1029/2020JA028354