Statistical Study on Suprathermal Electrons in the Inner Magnetosphere

Abstract

Suprathermal electrons in the 0.1–10 keV energy range are responsible for Landau damping of whistler‐mode waves in the inner magnetosphere. In this study, we perform a statistical survey on the spatial and temporal distributions of suprathermal electrons using observations from the Van Allen Probes (VAP). The results are systematically compared with both a long‐term THEMIS dataset spanning 2007–2024 and the earlier study of W. Li et al. (2010, https://doi.org/10.1029/2010ja015687 ) based on limited THEMIS dataset. Both VAP and THEMIS show similar levels of electron flux enhancement near the plasma sheet source region during active geomagnetic conditions, while the VAP dataset exhibits steeper electron phase space density (PSD) spectra outside the plasmasphere. We find that both the VAP and long‐term THEMIS datasets exhibit systematically higher suprathermal electron fluxes inside the plasmasphere at L  > 3 near dusk sector than those reported by W. Li et al. (2010, https://doi.org/10.1029/2010ja015687 ). The availability of corrections for proton contamination allows VAP to improve coverage to lower ‐shells inside the plasmasphere. Possible contributions from ionospheric photoelectrons inside the plasmasphere are discussed. We construct a new empirical model of suprathermal electrons by applying power‐law fits to the PSD in MLT‐Lshell maps under different geomagnetic conditions. Using this empirical model, we evaluate characteristic linear Landau damping rates of whistler‐mode waves at representative locations in the inner magnetosphere. The resulting model provides key parameters for quantifying Landau damping effect of whistler‐mode wave propagation in the magnetosphere.