Journal article
Whistler anisotropy instabilities as the source of banded chorus: Van Allen Probes observations and particle‐in‐cell simulations
Journal of geophysical research. Space physics, Vol.119(10), pp.8288-8298
10/2014
DOI: 10.1002/2014JA020364
PMCID: PMC4497467
PMID: 26167433
Abstract
Magnetospheric banded chorus is enhanced whistler waves with frequencies ωr<Ωe, where Ωe is the electron cyclotron frequency, and a characteristic spectral gap at ωr≃Ωe/2. This paper uses spacecraft observations and two‐dimensional particle‐in‐cell simulations in a magnetized, homogeneous, collisionless plasma to test the hypothesis that banded chorus is due to local linear growth of two branches of the whistler anisotropy instability excited by two distinct, anisotropic electron components of significantly different temperatures. The electron densities and temperatures are derived from Helium, Oxygen, Proton, and Electron instrument measurements on the Van Allen Probes A satellite during a banded chorus event on 1 November 2012. The observations are consistent with a three‐component electron model consisting of a cold (a few tens of eV) population, a warm (a few hundred eV) anisotropic population, and a hot (a few keV) anisotropic population. The simulations use plasma and field parameters as measured from the satellite during this event except for two numbers: the anisotropies of the warm and the hot electron components are enhanced over the measured values in order to obtain relatively rapid instability growth. The simulations show that the warm component drives the quasi‐electrostatic upper band chorus and that the hot component drives the electromagnetic lower band chorus; the gap at ∼Ωe/2 is a natural consequence of the growth of two whistler modes with different properties.
Key PointsThe frequency gas of banded chorus is explained by linear dispersion theoryBanded chorus is excited by two distinct anisotropic electron componentsTheory, simulations, and observations agree
Details
- Title: Subtitle
- Whistler anisotropy instabilities as the source of banded chorus: Van Allen Probes observations and particle‐in‐cell simulations
- Creators
- Xiangrong Fu - Los Alamos National LaboratoryMisa M Cowee - Los Alamos National LaboratoryReinhard H Friedel - Los Alamos National LaboratoryHerbert O Funsten - Los Alamos National LaboratoryS. Peter Gary - Space Science InstituteGeorge B Hospodarsky - University of IowaCraig Kletzing - University of IowaWilliam Kurth - University of IowaBrian A Larsen - Los Alamos National LaboratoryKaijun Liu - Auburn UniversityElizabeth A MacDonald - Goddard Space Flight CenterKyungguk Min - Auburn UniversityGeoffrey D Reeves - Los Alamos National LaboratoryRuth M Skoug - Los Alamos National LaboratoryDan Winske - Los Alamos National Laboratory
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.119(10), pp.8288-8298
- DOI
- 10.1002/2014JA020364
- PMID
- 26167433
- PMCID
- PMC4497467
- NLM abbreviation
- J Geophys Res Space Phys
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 11
- Grant note
- DOI: 10.13039/100000104, name: National Aeronautics and Space Administration, award: NAS5-01072; DOI: 10.13039/100000104, name: National Aeronautics and Space Administration, award: NNX14AD62G; DOI: 10.13039/100000001, name: National Science Foundation, award: AGS-1303300
- Language
- English
- Date published
- 10/2014
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199839802771
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