Global Survey and Empirical Model of Fast Magnetosonic Waves Over Their Full Frequency Range in Earth's Inner Magnetosphere

Q. Ma, W. Li, J. Bortnik, C. A. Kletzing, W. S. Kurth, G. B. Hospodarsky, J. R. Wygant

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3 Scopus citations

Abstract

We investigate the global distribution and provide empirical models of fast magnetosonic waves using the combined observations by the magnetometer and waveform receiver on board Van Allen Probes. The magnetometer measurements of magnetosonic waves indicate a significant wave power within the frequency range from the helium gyrofrequency to 20 Hz at L ≥ 4 in the afternoon sector, both inside and outside the plasmapause. The waveform receiver measurements indicate a significant wave power from 20 Hz to the lower hybrid resonance frequency at L ≤ 5.5 near the dayside outside the plasmapause or in the afternoon sector inside the plasmapause. The sum of the wave powers from the two instruments provides the wave power distribution over the complete frequency range. The most significant root-mean-square wave amplitude of magnetosonic waves is typically 100–200 pT inside or outside the plasmapause with a magnetic local time coverage of 30–50% during geomagnetically active times when AE* > 500 nT. The magnetosonic wave frequency increases with decreasing L shell following the trend of the proton gyrofrequency outside the plasmapause, indicating a close relation with the local wave generation. Inside the plasmapause, the dependence of wave frequency on L shell is weaker, and the wave frequency is more stable across L shells, indicating the wave propagation effects from the source located at higher L shells. We have performed polynomial fits of the global magnetosonic wave distribution and wave frequency spectra, which are useful in future radiation belt simulations.

Original languageEnglish (US)
Pages (from-to)10270-10282
Number of pages13
JournalJournal of Geophysical Research: Space Physics
Volume124
Issue number12
DOIs
StatePublished - Dec 1 2019

Bibliographical note

Funding Information:
This work was supported by RBSP‐ECT and EMFISIS funding provided by JHU/APL Contract 967399 and 921647 under NASA's Prime Contract NAS5‐01072. The analysis at UCLA was supported by NASA Grants NNX16AG21G, NNX15AI96G, NNX14AN85G, and NNX14AI18G. Q. M. would like to acknowledge the NASA Grant 80NSSC20K0196. W. L. would like to acknowledge the AFOSR Grant FA9550‐15‐1‐0158, NSF Grant AGS‐1847818, and the Alfred P. Sloan Research Fellowship FG‐2018‐10936. We acknowledge the Van Allen probes data from the EMFISIS instrument obtained from http://emfisis.physics.uiowa.edu/Flight/ , data from the EFW instrument are obtained from http://rbsp.space.umn.edu/data/rbsp/ , and geomagnetic AE index obtained from http://wdc.kugi.kyoto‐u.ac.jp/aedir/ . The processed data are available at the data repository https://doi.org/10.6084/m9.figshare.9820400.v1 . We acknowledge Richard M. Thorne for his support and helpful comments.

Funding Information:
This work was supported by RBSP-ECT and EMFISIS funding provided by JHU/APL Contract 967399 and 921647 under NASA's Prime Contract NAS5-01072. The analysis at UCLA was supported by NASA Grants NNX16AG21G, NNX15AI96G, NNX14AN85G, and NNX14AI18G. Q. M. would like to acknowledge the NASA Grant?80NSSC20K0196.?W. L. would like to acknowledge the AFOSR Grant FA9550-15-1-0158, NSF Grant AGS-1847818, and the Alfred P. Sloan Research Fellowship FG-2018-10936. We acknowledge the Van Allen probes data from the EMFISIS instrument obtained from http://emfisis.physics.uiowa.edu/Flight/, data from the EFW instrument are obtained from http://rbsp.space.umn.edu/data/rbsp/, and geomagnetic AE index obtained from http://wdc.kugi.kyoto-u.ac.jp/aedir/. The processed data are available at the data repository https://doi.org/10.6084/m9.figshare.9820400.v1. We acknowledge Richard M. Thorne for his support and helpful comments.

Publisher Copyright:
©2019. American Geophysical Union. All Rights Reserved.

Keywords

  • Empirical Fitting
  • Global Survey
  • Magnetosonic Waves
  • Van Allen Probes Observation

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