We conduct a global survey of magnetosonic waves and compute the associated bounce and drift averaged diffusion coefficients, taking into account co-located measurements of fpe/fce, to assess the role of magnetosonic waves in radiation belt dynamics, where fpe is the plasma frequency and fce is the electron gyrofrequency.. The average magnetosonic wave intensities increase with increasing geomagnetic activity and decreasing relative frequency with the majority of the wave power in the range fcp < f < 0.3fLHR during active conditions, where fcp is the proton gyrofrequency and fLHR is the lower hybrid resonance frequency. In the region 4.0 <= L* <= 5.0, the bounce and drift averaged energy diffusion rates due to magnetosonic waves never exceed those due to whistler mode chorus, suggesting that whistler mode chorus is the dominant mode for electron energisation to relativistic energies in this region. Further in, in the region 2.0 <= L* <= 3.5, the bounce and drift averaged pitch angle diffusion rates due to magnetosonic waves can exceed those due to plasmaspheric hiss and very low frequency (VLF) transmitters over energy-dependent ranges of intermediate pitch angles. We compute electron lifetimes by solving the 1D pitch angle diffusion equation including the effects of plasmaspheric hiss, VLF transmitters and magnetosonic waves. We find that magnetosonic waves can have a significant effect on electron loss timescales in the slot region reducing the loss timescales during active times from 5.6 to 1.5 days for 500 keV electrons at L* = 2.5 and from 140.4 days to 35.7 days for 1 MeV electrons at L* = 2.0.
The research leading to these results has received funding from the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 (Sat-Risk) and NE/R016038/1.
Electron Diffusion, Magnetosonic Waves, Radiation Belts
Wong, J. (2022). Electron Diffusion by Magnetosonic Waves in the Earth's Radiation Belts (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/aae6ea2f-7dab-4ab1-830f-a4c53589e340
Wong, J.-M., Meredith, N. P., Horne, R. B., Glauert, S. A., & Ross, J. P. J., Electron Diffusion by Magnetosonic Waves in the Earth's Radiation Belts, JGR Space Physics, (https://doi.org/10.1029/2021JA030196), 2022.
The wave data have been calibrated and quality-controlled prior to release. We also omitted data during thruster firing, eclipse and charging times.
The data for the figures and generation of the diffusion coefficients come from the EMFISIS instrument on Van Allen Probes RBSP-A available online (https://emfisis.physics.uiowa.edu/data/index). The Kp indices used in this study are available from the NSSDC Omniweb. Full details of the subsequent analysis are given in Wong et al 
We use data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instruments on board RBSP-A. The EMFISIS Waveform Receivers on RBSP-A measured the sum of the three components of the magnetic power spectral density of the waves in 65 frequency channels, with centre frequencies between 2.13 Hz and 11.24 kHz. We also use density measurements from the EMFISIS High Frequency Receiver which measured the electric field power spectral density in the frequency range 10 kHz to 487 kHz.