Abstract
Current-driven instabilities in forced current sheets
Current-driven instabilities in forced current sheets
M. I. Sitnov
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland, USA
A. T. Y. Lui
Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA
P. N. Guzdar
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland, USA
P. H. Yoon
Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, USA
The nonlocal kinetic linear stability analysis of the non-Harris thin current sheet equilibrium, namely the thin current sheet
embedded in a thicker anisotropic plasma sheet [
Sitnov et al., 2000a
,
2000b], with respect to current-driven instabilities is performed using the finite element technique. In contrast to the Harris
sheet, the new equilibrium becomes possible due to the plasma anisotropy outside the sheet caused by two warm counterstreaming
field-aligned beams and complex ion orbits that cannot be described in such thin current sheets in terms of the conventional
magnetic moment. It is found that in contrast to the case of the Harris sheet, the analogs of the drift-kink instability in
these current sheets can have significant growth rates for the realistic ion-to-electron mass and temperature ratios. The
unstable modes share the properties with both the lower-hybrid and drift-kink modes. In particular, the unstable modes resemble
the lower-hybrid drift modes as they are more highly structured across the sheet than the drift-kink instability (DKI) and
assume both odd (DKI-like) and even parity solutions. On the other hand, in contrast to the lower-hybrid drift instability
(LHDI) and like the DKI, the unstable modes have much larger wavelength, electromagnetic component, and significantly perturb
the central current region. The possible role of the current-driven instabilities in magnetic reconnection and magnetic annihilation
as well as the geophysical implications such as the current disruption in the geomagnetotail during substorms are also discussed.
Received 8
July
2003;
accepted 31
December
2003;
published 11
March
2004.
Citation: Sitnov, M. I., A. T. Y. Lui, P. N. Guzdar, and P. H. Yoon
(2004),
Current-driven instabilities in forced current sheets,
J. Geophys. Res.,
109,
A03205,
doi:10.1029/2003JA010123.