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Study of EMIC wave excitation using direct ion measurements


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dc.contributorKyungguk Min, kmin@auburn.eduen_US
dc.creatorMin, Kyungguk
dc.creatorLiu, Kaijun
dc.creatorWygant, John R.
dc.date.accessioned2020-06-05T15:46:58Z
dc.date.available2020-06-05T15:46:58Z
dc.date.created2015-04
dc.identifier10.1002/2014JA020717en_US
dc.identifier.urihttps://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JA020717en_US
dc.identifier.urihttp://hdl.handle.net/11200/49852
dc.description.abstractWith data from Van Allen Probes, we investigate electromagnetic ion cyclotron (EMIC) wave excitation using simultaneously observed ion distributions. Strong He band waves occurred while the spacecraft was moving through an enhanced density region. We extract from helium, oxygen, proton, and electron mass spectrometer measurement the velocity distributions of warm heavy ions as well as anisotropic energetic protons that drive wave growth through the ion cyclotron instability. Fitting the measured ion fluxes to multiple sin(m)-type distribution functions, we find that the observed ions make up about 15% of the total ions, but about 85% of them are still missing. By making legitimate estimates of the unseen cold (below approximate to 2eV) ion composition from cutoff frequencies suggested by the observed wave spectrum, a series of linear instability analyses and hybrid simulations are carried out. The simulated waves generally vary as predicted by linear theory. They are more sensitive to the cold O+ concentration than the cold He+ concentration. Increasing the cold O+ concentration weakens the He band waves but enhances the O band waves. Finally, the exact cold ion composition is suggested to be in a range when the simulated wave spectrum best matches the observed one.en_US
dc.formatPDFen_US
dc.publisherAMER GEOPHYSICAL UNIONen_US
dc.relation.ispartofJOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICSen_US
dc.relation.ispartofseries2169-9380en_US
dc.subjectEMIC wave excitation; observation; linear theory and hybrid simulationen_US
dc.subjectCYCLOTRON WAVES; RING CURRENT; THERMAL PLASMA; H+-HE+; O+; INSTABILITIES; PARTICLE; AMPLIFICATION; GENERATION; ANISOTROPYen_US
dc.titleStudy of EMIC wave excitation using direct ion measurementsen_US
dc.typeTexten_US
dc.type.genreJournal Article, Academic Journalen_US
dc.citation.volume120en_US
dc.citation.issue4en_US
dc.citation.spage2702en_US
dc.citation.epage2719en_US
dc.description.statusPublisheden_US
dc.creator.orcid0000-0002-2095-8529en_US
dc.creator.orcid0000-0001-5882-1328en_US

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