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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, A02210, doi:10.1029/2003JA010180, 2004

Lower-hybrid-drift and modified-two-stream instabilities in current sheet equilibrium

Peter H. Yoon

Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, USA

Anthony T. Y. Lui

Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA

Abstract

The present article discusses the stability of the thin current sheet against lower-hybrid-drift (LHDI) and modified-two-stream (MTSI) instabilities. It is demonstrated that MTSI is driven by the cross-field current, implying that MTSI should also be most effective at the neutral sheet, while LHDI is driven by the density gradient, which is maximized near the edge of the current sheet. It is shown that under a normal Harris current sheet condition, V _i /∣V _e ∣ = T _i /T _e , LHDI completely dominates MTSI, which implies that linearly unstable current-driven modes cannot penetrate to the center of the Harris current sheet. However, if the Harris current sheet condition is relaxed to V _i /∣V _e ∣ > T _i /T _e , then MTSI is shown to gradually overtake LHDI. This finding indicates that cross-field drift linear instability dominated by MTSI feature may be operative at the center of the ion-dominated thin current sheet.

Received 4 August 2003; accepted 21 November 2003; published 19 February 2004.

Index Terms: 2772 Magnetospheric Physics: Plasma waves and instabilities; 2764 Magnetospheric Physics: Plasma sheet; 2744 Magnetospheric Physics: Magnetotail; 2788 Magnetospheric Physics: Storms and substorms; 7871 Space Plasma Physics: Waves and instabilities.

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Citation: Yoon, P. H., and A. T. Y. Lui (2004), Lower-hybrid-drift and modified-two-stream instabilities in current sheet equilibrium, J. Geophys. Res., 109, A02210, doi:10.1029/2003JA010180.

Copyright 2004 by the American Geophysical Union.