Ion cyclotron waves at Titan
File(s)
Author(s)
Russell, CT
Wei, HY
Cowee, MM
Neubauer, FM
Dougherty, MK
Type
Journal Article
Abstract
During the interaction of Titan's thick atmosphere with the ambient plasma, it was expected that ion cyclotron waves would be generated by the free energy of the highly anisotropic velocity distribution of the freshly ionized atmospheric particles created in the interaction. However, ion cyclotron waves are rarely observed near Titan, due to the long growth times of waves associated with the major ion species from Titan's ionosphere, such as CH4+ and N2+. In the over 100 Titan flybys obtained by Cassini to date, there are only two wave events, for just a few minutes during T63 flyby and for tens of minutes during T98 flyby. These waves occur near the gyrofrequencies of proton and singly ionized molecular hydrogen. They are left-handed, elliptically polarized, and propagate nearly parallel to the field lines. Hybrid simulations are performed to understand the wave growth under various conditions in the Titan environment. The simulations using the plasma and field conditions during T63 show that pickup protons with densities ranging from 0.01 cm−3 to 0.02 cm−3 and singly ionized molecular hydrogens with densities ranging from 0.015 cm−3 to 0.25 cm−3 can drive ion cyclotron waves with amplitudes of ~0.02 nT and of ~0.04 nT within appropriate growth times at Titan, respectively. Since the T98 waves were seen farther upstream than the T63 waves, it is possible that the instability was stronger and grew faster on T98 than T63.
Date Issued
2016-02-18
Date Acceptance
2016-02-15
Citation
Journal of Geophysical Research: Space Physics, 2016, 121 (3), pp.2095-2103
ISSN
2169-9402
Publisher
American Geophysical Union
Start Page
2095
End Page
2103
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
121
Issue
3
Copyright Statement
© 2016 American Geophysical Union. All Rights Reserved.
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Publication Status
Published