Generation of whistler mode emissions in the inner magnetosphere: An event study

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dc.contributor.authorSchriver, D.
dc.contributor.authorAshour-Abdalla, M.
dc.contributor.authorCoroniti, F. V.
dc.contributor.authorLeBoeuf, J. N.
dc.contributor.authorDecyk, V.
dc.contributor.authorTravnicek, P.
dc.contributor.authorSantolík, O.
dc.contributor.authorWinningham, D.
dc.contributor.authorPickett, J. S.
dc.contributor.authorGoldstein, Melvyn
dc.contributor.authorFazakerley, A. N.
dc.date.accessioned2023-11-21T16:23:21Z
dc.date.available2023-11-21T16:23:21Z
dc.date.issued2010-08-21
dc.description.abstractOn July 24, 2003, when the Cluster 4 satellite crossed the magnetic equator at about 4.5 RE radial distance on the dusk side (∼15 MLT), whistler wave emissions were observed below the local electron gyrofrequency (fcₑ) in two bands, one band above one-half the gyrofrequency (0.5fcₑ) and the other band below 0.5fcₑ. A careful analysis of the wave emissions for this event has shown that Cluster 4 passed through the wave source region. Simultaneous electron particle data from the PEACE instrument in the generation region indicated the presence of a mid-energy electron population (∼100 s of eV) that had a highly anisotropic temperature distribution with the perpendicular temperature 10 times the parallel temperature. To understand this somewhat rare event in which the satellite passed directly through the wave generation region and in which a free energy source (i.e., temperature anisotropy) was readily identified, a linear theory and particle in cell simulation study has been carried out to elucidate the physics of the wave generation, wave-particle interactions, and energy redistribution. The theoretical results show that for this event the anisotropic electron distribution can linearly excite obliquely propagating whistler mode waves in the upper frequency band, i.e., above 0.5fcₑ. Simulation results show that in addition to the upper band emissions, nonlinear wave-wave coupling excites waves in the lower frequency band, i.e., below 0.5fce. The instability saturates primarily by a decrease in the temperature anisotropy of the mid-energy electrons, but also by heating of the cold electron population. The resulting wave-particle interactions lead to the formation of a high-energy plateau on the parallel component of the warm electron velocity distribution. The theoretical results for the saturation time scale indicate that the observed anisotropic electron distribution must be refreshed in less than 0.1 s allowing the anisotropy to be detected by the electron particle instrument, which takes several seconds to produce a distribution.
dc.description.sponsorshipThe authors wish to thank R. Richard for useful comments concerning this study. This work was supported by NASA GI grant NNX08AF26G and a NASA GSFC grant NNX07AJ86G. Work at the University of Iowa was carried out under NASA GSFC grant NNX07AI24G. O.S. acknowledges the support of grant KONTAKT ME842. Computing was carried out on the NAS SGI Altix machine as part of the Columbia supercomputing system and the NSF NCAR Frost Blue Gene supercomputing system.
dc.description.urihttps://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009JA014932
dc.format.extent13 pages
dc.genrejournal articles
dc.identifier.citationSchriver, D., et al. (2010), Generation of whistler mode emissions in the inner magnetosphere: An event study, J. Geophys. Res., 115, A00F17, doi:10.1029/2009JA014932.
dc.identifier.urihttps://doi.org/10.1029/2009JA014932
dc.identifier.urihttp://hdl.handle.net/11603/30816
dc.language.isoen_US
dc.publisherAGU
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Goddard Planetary Heliophysics Institute (GPHI)
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rightsPublic Domain Mark 1.0
dc.rights.urihttps://creativecommons.org/publicdomain/mark/1.0/
dc.titleGeneration of whistler mode emissions in the inner magnetosphere: An event study
dc.typeText
dcterms.creatorhttps://orcid.org/0000-0002-5317-988X

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