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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 32, issue 7
Ann. Geophys., 32, 889–898, 2014
https://doi.org/10.5194/angeo-32-889-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 32, 889–898, 2014
https://doi.org/10.5194/angeo-32-889-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

ANGEO Communicates 31 Jul 2014

ANGEO Communicates | 31 Jul 2014

Effects of cold electron number density variation on whistler-mode wave growth

R. Tang1,2,3, D. Summers3, and X. Deng1 R. Tang et al.
  • 1Institute of Space Science and Technology, Nanchang University, Nanchang, 330031, China
  • 2State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China
  • 3Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland, Canada

Abstract. We examine how the growth of magnetospheric whistler-mode waves depends on the cold (background) electron number density N0. The analysis is carried out by varying the cold-plasma parameter a = (electron gyrofrequency)2/(electron plasma frequency)2 which is proportional to 1/N0. For given values of the thermal anisotropy AT and the ratio Nh/N0, where Nh is the hot (energetic) electron number density, we find that, as N0 decreases, the maximum values of the linear and nonlinear growth rates decrease and the threshold wave amplitude for nonlinear growth increases. Generally, as N0 decreases, the region of (Nh/N0, AT)-parameter space in which nonlinear wave growth can occur becomes more limited; that is, as N0 decreases, the parameter region permitting nonlinear wave growth shifts to the top right of (Nh/N0, AT) space characterized by larger Nh/N0 values and larger AT values. The results have implications for choosing input parameters for full-scale particle simulations and also in the analysis of whistler-mode chorus data.

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