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Nondiffusive Pitch-Angle Scattering of a Distribution of Energetic Particles by Coherent Whistler Waves

Yoon, Young Dae and Bellan, Paul M. (2020) Nondiffusive Pitch-Angle Scattering of a Distribution of Energetic Particles by Coherent Whistler Waves. Journal of Geophysical Research. Space Physics, 125 (6). Art. No. e2020JA027796. ISSN 2169-9380. https://resolver.caltech.edu/CaltechAUTHORS:20200612-083600424

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Abstract

Whether or not coherent magnetospheric whistler waves play important roles in the pitch‐angle scattering of energetic particles is a crucial question in magnetospheric physics. The interaction of a thermal distribution of energetic particles with coherent whistler waves is thus investigated. The distribution is prescribed by the Maxwell‐Jüttner distribution, which is a relativistic generalization of the Maxwell‐Boltzmann distribution. Coherent whistler waves are modeled by circularly polarized waves propagating parallel to the background magnetic field. It is shown that for parameters relevant to magnetospheric chorus, a significant fraction (1‐5%) of the energetic particle population undergoes drastic, non‐diffusive pitch‐angle scattering by coherent chorus. The scaling of this fraction with the wave amplitude may also explain the association of relativistic microbursts to large‐amplitude chorus. A much improved condition for large pitch‐angle scattering is presented that is related to, but may or may not include the exact resonance condition depending on the particle's initial conditions. The theory reveals a critical mechanism not contained in the widely‐used second‐order trapping theory.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2020ja027796DOIArticle
https://doi.org/10.22002/D1.1333DOIData
ORCID:
AuthorORCID
Yoon, Young Dae0000-0001-8394-2076
Bellan, Paul M.0000-0002-0886-8782
Alternate Title:Non-diffusive pitch‐angle scattering of a distribution of energetic particles by coherent whistler waves
Additional Information:© 2020 American Geophysical Union. Version of Record online: 17 June 2020. Accepted manuscript online: 11 June 2020; Manuscript accepted: 05 May 2020; Manuscript revised: 30 April 2020; Manuscript received: 10 January 2020. The authors thank Mackenzie Wooten for reproducing some of the initial algebra. This material is based upon work supported by the Air Force Office of Scientific Research under award No. FA9550-17-1-0023 and by the NSF Division of Atmospheric and Geospace Sciences under award No. 1914599. The associated scripts that generate data and plots for this paper are available online (https://doi.org/10.22002/D1.1333).
Funders:
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-17-1-0023
NSFAGS-1914599
Subject Keywords:Whistler Wave; Energetic Particles; Pitch‐Angle Scattering
Issue or Number:6
Record Number:CaltechAUTHORS:20200612-083600424
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200612-083600424
Official Citation:Yoon, Y. D., & Bellan, P. M. ( 2020). Nondiffusive pitch‐angle scattering of a distribution of energetic particles by coherent whistler waves. Journal of Geophysical Research: Space Physics, 125, e2020JA027796. https://doi.org/10.1029/2020JA027796
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103863
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Jun 2020 17:19
Last Modified:24 Jun 2020 15:00

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