Suprathermal Electron Acceleration at the Earth's Bow Shock: Simulations and Observations

Liu et al. (2020, https://doi.org/10.3847/2041-8213/ab64d0, ApJ, 935, 39) conducted observational study with Magnetospheric Multiscale (MMS) data to characterize bow shock events, analyzing shock parameters, electron flux/energy spectra (double-power-law with break energy), PADs, and energy-dependent drift dynamics to confirm shock-drift acceleration (SDA) dominance. This paper presents simulations of solar wind suprathermal electron acceleration at Earth's bow shock, compared with in situ observations from the MMS mission on 4 November 2015. The event involves a quasi-perpendicular shock crossing (Formula presented.) below the subsolar point. Using test-particle simulations, we derive pitch-angle distributions (PADs) across 12 energy channels (0.295–25.924 keV), demonstrating robust consistency between modeled and observed electron fluxes—validating our model for bow shock particle acceleration studies. Key findings include: (a) Downstream-to-upstream flux ratios peak near (Formula presented.) pitch angle, indicating SDA dominance. (b) Omnidirectional energy spectra exhibit a double-power-law with a break at 40 keV; spectral indices of 2.8 (below) and 5.4 (above) align with observations. (c) SDA analysis (drift velocity, length, and time) confirms the mechanism's prevalence. These results demonstrate the physical consistency of our model and the observational findings of Liu et al.