Short Chorus Wave Packets: Generation Within Chorus Elements, Statistics, and Consequences on Energetic Electron Precipitation

• Published in: Journal of geophysical research. Space physics Vol. 127; no. 5; pp. e2022JA030310 - n/a
• Main Authors: Mourenas, D., Zhang, X.‐J., Nunn, D., Artemyev, A. V., Angelopoulos, V., Tsai, E., Wilkins, C.
• Format: Journal Article
• Language: English
• Published: United States 01.05.2022
• Subjects: anomalous trapping; chorus wave; nonlinear generation; quasi‐linear diffusion; wave beating; wave superposition; wave beating; chorus wave; nonlinear generation; anomalous trapping; quasi‐linear diffusion; wave superposition
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2022JA030310

Short and intense lower‐band chorus wave packets are ubiquitous in the Earth's outer radiation belt. In this article, we perform various Vlasov hybrid simulations, with one or two triggering waves, to study the generation of short chorus packets/subpackets inside long rising tone elements. We show that the length of the generated short wave packets is consistent with a criterion of resonance non‐overlap for two independent superposed waves, and that these chorus packets have similar characteristics as in Van Allen Probes observations. We find that short wave packets are mainly formed near the middle/end of long rising tones for moderate linear growth rates, and everywhere for stronger linear growth rates. Finally, we analyze an event characterized by Time History of Events and Macroscale Interactions during Substorms spacecraft measurements of chorus rising tones near the equator and simultaneous measurements by low altitude ELFIN CubeSats of precipitating and trapped electron fluxes in the same sector. The measured precipitating electron fluxes are well recovered by test particle simulations performed using measured plasma and wave properties. We show that short chorus wave packets of moderate amplitudes (160–250 pT) essentially lead to a more diffusive‐like transport of 50–200 keV electrons toward the loss cone than long packets. In contrast, long chorus packets are found to produce important nonlinear effects via anomalous trapping, which significantly reduces electron precipitation below 150 keV, especially for higher wave amplitudes. Key Points Vlasov hybrid simulations consistently produce short chorus packets by wave superposition, with similar characteristics as in observations Short chorus wave packets are found in the middle/end of rising tones for low linear growth rates but everywhere for high growth rates Electron precipitation by short moderate amplitude chorus wave packets occurs in a nearly quasi‐linear regime