Three‐Dimensional Simulations of Ultra‐Relativistic Electron Acceleration During the 21 April 2017 Storm

Abstract

The acceleration mechanisms of ultra‐relativistic electrons (>∼5 MeV) have received more and more attention in the Van Allen Probes era. Both chorus waves and radial diffusion are considered capable of accelerating ultra‐relativistic electrons, and their roles in acceleration still under debate today. In this study, we present 3‐D simulations for evaluating the evolutions of ultra‐relativistic electron phase space density (PSD) during a weak storm on April 2017. Comparison of simulation results with observations suggests that local peaks in PSD profile of ultra‐relativistic electrons are generated by chorus waves, then smoothed and widened due to the transport of electrons from the peak to either side by radial diffusion. Chorus waves act dominantly in the acceleration of ultra‐relativistic electrons while radial diffusion assists. We also found that radial diffusion coefficient model of W. Liu et al. (2016, https://doi.org/10.1002/2015GL067398) is more suitable and reasonable than model of Brautigam and Albert (2000, https://doi.org/10.1029/1999JA900344) for 3‐D simulation of ultra‐relativistic electrons. A more accurate radial diffusion coefficient model is vital and demanded for quantitatively evaluating the contribution of these two mechanisms for ultra‐relativistic electrons acceleration in the future.

Ultra-relativistic Electron Acceleration during High-intensity Long-duration Continuous Auroral Electrojet Activity Events

“…Earlier works have demonstrated case-to-case variations in the dominant roles played by radial diffusion (Zong et al 2009;Ali et al 2016;Jaynes et al 2018;Ozeke et al 2020) and local acceleration (Thorne 2010;Reeves et al 2013;Thorne et al 2013;Li et al 2014;Xiao et al 2014;Allison & Shprits 2020;Guo et al 2021). The combined impacts of both the mechanisms (Baker et al 2014;Zhao et al 2019;Guo et al 2023) and energy-dependent acceleration mechanisms (Foster et al 2014;Kanekal et al 2015;Li et al 2016;Zhao et al 2018) have also been discussed.…”

Influences of Solar Wind Parameters on Energetic Electron Fluxes at Geosynchronous Orbit Revealed by the Deep SHAP Method

“…These satellites are exposed to a potential hazard environment filled with energetic electrons. The energetic electron fluxes can vary over several orders within a short period during geomagnetic activity times Guo et al, 2021Guo et al, , 2023Shin et al, 2016;Thorne, 2010;Wang et al, 2023;Xiang et al, 2021). Energetic electrons can cause irreversible damage on satellites including deep medium charging and single event upset (Liu et al, 2021;Novikov et al, 2008;Pilipenko et al, 2006;Y.…”