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Proton velocity ring-driven instabilities in the inner magnetosphere: Linear theory and particle-in-cell simulations


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dc.contributorKyungguk Min, kmin@auburn.eduen_US
dc.creatorMin, Kyungguk
dc.creatorLiu, Kaijun
dc.date.accessioned2022-09-29T14:55:18Z
dc.date.available2022-09-29T14:55:18Z
dc.date.created2016
dc.identifier10.1002/2015JA022042en_US
dc.identifier.urihttps://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JA022042en_US
dc.identifier.urihttps://aurora.auburn.edu/handle/11200/50354
dc.identifier.urihttp://dx.doi.org/10.35099/aurora-422
dc.description.abstractLinear dispersion theory and electromagnetic particle-in-cell (PIC) simulations are used to investigate linear growth and nonlinear saturation of the proton velocity ring-driven instabilities, namely, ion Bernstein instability and Alfven-cyclotron instability, which lead to fast magnetosonic waves and electromagnetic ion cyclotron waves in the inner magnetosphere, respectively. The proton velocity distribution is assumed to consist of 10% of a ring distribution and 90% of a low-temperature Maxwellian background. Here two cases with ring speeds v(r)/v(A)=1 and 2 (v(A) is the Alfven speed) are examined in detail. For the two cases, linear theory predicts that the maximum growth rate (m) of the Bernstein instability is 0.16(p) and 0.19(p), respectively, and (m) of the Alfven-cyclotron instability is 0.045(p) and 0.15(p), respectively, where (p) is the proton cyclotron frequency. Two-dimensional PIC simulations are carried out for the two cases to examine the instability development and the corresponding evolution of the particle distributions. Initially, Bernstein waves develop and saturate with strong electrostatic fluctuations. Subsequently, electromagnetic Alfven-cyclotron waves grow and saturate. Despite their smaller growth rate, the saturation levels of the Alfven-cyclotron waves for both cases are larger than those of the Bernstein waves. Resonant interactions with the Bernstein waves lead to scattering of ring protons predominantly along the perpendicular velocity component (toward both decreasing and, at a lesser extent, increasing speeds) without substantial change of either the parallel temperature or the temperature anisotropy. Consequently, the Alfven-cyclotron instability can still grow. Furthermore, the free energy resulting from the pitch angle scattering by the Alfven-cyclotron waves is larger than the free energy resulting from the perpendicular energy scattering, thereby leading to the larger saturation level of the Alfven-cyclotron waves.en_US
dc.formatPDFen_US
dc.relation.ispartofseries2169-9380en_US
dc.rights©American Geophysical Union 2016. This is this the version of record co-published by the American Geophysical Union and John Wiley & Sons, Inc. It is made available under the CC-BY-NC-ND 4.0 license. Item should be cited as: Min, Kyungguk, and Kaijun Liu. "Proton velocity ring‐driven instabilities in the inner magnetosphere: Linear theory and particle‐in‐cell simulations." Journal of Geophysical Research: Space Physics 121.1 (2016): 475-491.en_US
dc.titleProton velocity ring-driven instabilities in the inner magnetosphere: Linear theory and particle-in-cell simulationsen_US
dc.typeTexten_US
dc.type.genreJournal Article, Academic Journalen_US
dc.citation.volume121en_US
dc.citation.issue1en_US
dc.citation.spage475en_US
dc.citation.epage491en_US
dc.description.statusPublisheden_US
dc.description.peerreviewYesen_US
dc.creator.orcid0000-0001-5882-1328en_US

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