DOI: 10.5285/fa63faf5-10d6-4c72-8b19-d41941f06812
title: New Chorus Diffusion Coefficients for Radiation Belt Modelling

description: Whistler mode chorus is an important magnetospheric wave emission playing a major role in radiation belt dynamics, where it contributes to both the acceleration and loss of relativistic electrons. In this study we compute bounce and drift averaged chorus diffusion coefficients for 3.0 &lt; L* &lt; 6.0, using the TS04 external magnetic field model, taking into account co-located near-equatorial measurements of the wave intensity and fpe/fce, by combining the Van Allen probes measurements with data from a multi-satellite VLF wave database. The variation of chorus wave normal angle with spatial location and fpe/fce is also taken into account. We find that chorus propagating at small wave normal angles has the dominant contribution to the diffusion rates in most MLT sectors. However, in the region 4 &lt;= MLT &lt; 11 high wave normal angles dominate at intermediate pitch angles. In the region 3 &lt; L* &lt; 4, the bounce and drift averaged pitch angle and energy diffusion rates during active conditions are primarily larger than those in our earlier models by up to a factor of 10 depending on energy and pitch angle. Further out, the results are similar. We find that the bounce and drift averaged energy and pitch angle diffusion rates can be significantly larger than the new model in regions of low fpe/fce,eq, where the differences can be up to a factor of 10 depending on energy and pitch angle. Funding was provided by the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 (Sat-Risk), NE/R016038/1 and NE/X000389/1.
description: 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), and the VLF database derived in Meredith et al [2020]. 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 [2023]
description: 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. Th VLF database contains wave data from eight satellites, including approximately 3 years of data from Dynamics Explorer 1 (DE1), 1 year of data from Double Star TC1, 10 years of data from Cluster 1, 8 years of data from each of Time History of Events and Macroscale Interactions during Substorms (THEMIS)-A, THEMIS-D, and THEMIS-E, and 3 years of data from the Van Allen probes RBSP-A and RBSP-B.
description: The wave data have been calibrated and quality-controlled prior to release. We also omitted data during thruster firing, eclipse and charging times.