Year: 2025
Type: article
Abstract: A statistical survey using 3 years of Van Allen Probes data from 2013 to 2015 is conducted to investigate the impact of broadband kinetic Alfvén waves (KAWs) on the pitch angle distributions (PADs) of relativistic electrons. 62 events exhibiting distinct KAW signatures, identified when other wave modes known to generate butterfly distributions were absent, are examined along with the corresponding PADs of electrons. The results reveal a relationship between the spectral energy density of KAWs and PAD of relativistic electrons, with butterfly PAD features becoming more pronounced and showing larger dip‐sizes as the spectral energy density of KAWs increases, particularly for electrons in 0.5–3.4 MeV energy range. At these times the magnetopause sub‐solar stand‐off distance renders magnetopause shadowing an unlikely formation mechanism. This suggests the interaction of relativistic electrons with broadband KAWs could be a significant mechanism, alongside drift‐shell splitting, contributing to the formation of butterfly PADs in the night‐side outer radiation belt of Earth.
Source: Geophysical Research Letters
DOI: 10.1029/2025gl115046
Authors: K. C. Barik, C. C. Chaston
Institutions: Space Sciences Laboratory, University of California, Berkeley
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,190
Funder: National Science Foundation
OpenAlex ID: W4410601614