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

Tao, X.; Thorne, R.M.; Horne, Richard B. ORCID: https://orcid.org/0000-0002-0412-6407; Grimald, S.; Arridge, C.S.; Hospodarsky, G.B.; Gurnett, D.A.; Coates, A.J.; Crary, F.J.. 2010 Excitation of electron cyclotron harmonic waves in the inner Saturn magnetosphere within local plasma injections. Journal of Geophysical Research, 115 (A12), A12204. 8, pp. 10.1029/2010JA015598

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Abstract/Summary

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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2010JA015598
Programmes:	BAS Programmes > Polar Science for Planet Earth (2009 - ) > Climate
ISSN:	0148-0227
Additional Keywords:	ECH waves, Saturnian magnetosphere, plasma injection, wave-particle interactions
NORA Subject Terms:	Space Sciences
Date made live:	05 Aug 2011 10:27 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/14841

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