Excitation of electron cyclotron harmonic waves in the inner Saturn magnetosphere within local plasma injections

被引:20
作者
Tao, X. [1 ]
Thorne, R. M. [1 ]
Horne, R. B. [6 ]
Grimald, S. [4 ,7 ]
Arridge, C. S. [2 ,8 ]
Hospodarsky, G. B. [5 ]
Gurnett, D. A. [5 ]
Coates, A. J. [2 ,8 ]
Crary, F. J. [3 ]
机构
[1] Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA 90095 USA
[2] Univ Coll London, Mullard Space Sci Lab, Dept Space & Climate Phys, Holmbury RH5 6NT, England
[3] SW Res Inst, San Antonio, TX 78288 USA
[4] Univ Toulouse 3, CNRS, Ctr Etud Spatiale Rayonnements, F-31028 Toulouse, France
[5] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA
[6] British Antarctic Survey, Cambridge CB3 0ET, England
[7] Univ Toulouse, Ctr Etud Spatiale Rayonnements, Toulouse, France
[8] UCL Birkbeck, Ctr Planetary Sci, London, England
基金
美国国家航空航天局;
关键词
IO TORUS; RADIO;
D O I
10.1029/2010JA015598
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Strong electron cyclotron harmonic (ECH) waves have been observed by Cassini associated with local plasma injection regions in the Saturnian magnetosphere. Using measured electron distributions from the Cassini plasma spectrometer, we calculated local growth rates and path-integrated wave gain of ECH waves inside an injection event using the HOTRAY code. We showed that electrons with energy near a few eV have a collision frequency comparable to their bounce frequency; thus, they cannot have an empty loss cone. We then demonstrated that the growth of ECH waves inside the injection event can be driven by electron phase space density gradients associated with the loss cone distribution of injected electrons at energies between a few hundred eV and a few keV. This conclusion is contrary to previous results that the source of free energy for growth of ECH waves is provided by electrons near a few eV. Results in this work are helpful for understanding the generation of ECH waves and their roles in electron dynamics in the Saturnian magnetosphere.
引用
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页数:8
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