2024/04/11 by Takanobu Amano, Miki Masuda, Amano, Takanobu +9 · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Earthquake Detection and Analysis #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Ionosphere and magnetosphere dynamics #Plasma Physics (physics.plasm-ph) #Solar and Space Plasma Dynamics #Space Physics (physics.space-ph)
paper · pdf · doi:10.48550/arxiv.2404.07404
openalex publication_date 2024/04/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We statistically investigate high-frequency whistler waves (with frequencies higher than ∼ 10 % of the local elect ron cyclotron frequency) at Earth's bow shock using Magnetospheric Multi-Scale (MMS) spacecraft observations. We focus specifically on the wave power within the shock transition layer, where we expect electron acceleration via stochastic sh ock drift acceleration (SSDA) to occur associated with efficient pitch-angle scattering by whistler waves. We find that the wave power is positively correlated with both the Alfvén Mach number in the normal incidence frame M\rm A and in the de Hoffmann-Teller frame M\rm A/cos θBn. The empirical relation with M\rm A/cos θBn is compared with the theory of SSDA that predicts a threshold wave power proportional to (M\rm A/cos θBn)-2. The result suggests that the wave power exceeds the theoretical threshold for M\rm A / cos θBn \gtrsim 30-60, beyond which efficient electron acceleration is expected. This aligns very well with previous statistical analysis of electron acceleration at Earth's bow shock (M. Oka, G eophys.~Res.~Lett., 33, 5, 2006). Therefore, we consider that this study provides further support for SSDA as the mechanism of electron acceleration at Earth's bow shock. At higher-Mach-number astrophysical shocks, SSDA will be able to inject electrons into the diffusive shock acceleration process for subsequent acceleration to cosmic-ray energies.