TITLE

Lower-hybrid drift and Buneman instabilities in current sheets with guide field

AUTHOR(S)
Yoon, P. H.; Lui, A. T. Y.
PUB. DATE
November 2008
SOURCE
Physics of Plasmas;11/1/2008, Vol. 15 Issue 11, p112105
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Lower-hybrid drift and Buneman instabilities operate in current sheets with or without the guide field. The lower-hybrid drift instability is a universal instability in that it operates for all parameters. In contrast, the excitation of Buneman instability requires sufficiently thin current sheet. That is, the relative electron-ion drift speed must exceed the threshold in order for Buneman instability to operate. Traditionally, the two instabilities were treated separately with different mathematical formalisms. In a recent paper, an improved electrostatic dispersion relation was derived that is valid for both unstable modes [P. H. Yoon and A. T. Y. Lui, Phys. Plasmas 15, 072101 (2008)]. However, the actual numerical analysis was restricted to a one-dimensional situation. The present paper generalizes the previous analysis and investigates the two-dimensional nature of both instabilities. It is found that the lower-hybrid drift instability is a flute mode satisfying k·B=0 and k·∇n=0, where k represents the wave number for the most unstable mode, B stands for the total local magnetic field, and ∇n is the density gradient. This finding is not totally unexpected. However, a somewhat surprising finding is that the Buneman instability is a field-aligned mode characterized by k×B=0 and k·∇n=0, rather than being a beam-aligned instability.
ACCESSION #
35541218

 

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