Measurability of the Nonlinear Response of Electron Distribution Function to Chorus Emissions in the Earth's Radiation Belt

0545648 - ÚFA 2022 RIV US eng J - Journal Article
Hanzelka, Miroslav - Santolík, Ondřej - Omura, Y. - Kolmašová, Ivana
Measurability of the Nonlinear Response of Electron Distribution Function to Chorus Emissions in the Earth's Radiation Belt.
Journal of Geophysical Research-Space Physics. Roč. 126, č. 9 (2021), č. článku e2021JA029624. ISSN 2169-9380. E-ISSN 2169-9402
EU Projects: European Commission(XE) 870452 - PAGER
Grant - others:AV ČR(CZ) JSPS-19-05
Program: Bilaterální spolupráce
Institutional support: RVO:68378289
Keywords : whistler-mode chorus * test particle simulation * nonlinear interaction * electromagnetic hole * particle measurements
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 3.111, year: 2021
Method of publishing: Open access
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021JA029624

We conduct test particle simulations to study the perturbations in a hot electron velocity distribution caused by a rising chorus element propagating parallel to the ambient magnetic field in the Earth's outer radiation belt. The wavefield is constructed from the nonlinear growth theory of chorus emissions of Omura (2021, https://doi.org/10.1186/s40623-021-01380-w), with additional considerations about saturation and propagation of the transverse resonant current being applied to model the subpacket structure. Using Liouville's theorem, we trace electrons back in time to reconstruct the evolution of electron velocity distribution at the magnetic equator. The electromagnetic hole created by nonlinear trapping and transport effects appears as a depression in the velocity distribution, aligned with the resonance velocity curve. We analyze the decrease of particle flux in this depression and estimate the energy resolution, pitch angle resolution, time resolution and geometric factor of particle analyzers needed to observe the perturbation. We conclude that particle detectors on current or recently operating spacecraft are always lacking in at least one of these parameters, which explains the missing direct observations of sharp phase space density depressions during chorus-electron nonlinear resonant interaction. However, with a dedicated experiment and appropriate measurement strategy, such observations are within the possibilities of the current technology. Similarity of the simulated density perturbation and a step function mathematical model is used to draw an analogy between the backward wave oscillator regime of chorus generation and the nonlinear growth theory.
Permanent Link: http://hdl.handle.net/11104/0322359