HR: 16:25h
AN: SH32C-02    [PDF]
TI: Ion-ion kink instability in the magnetotail: Linear Theory, Simulations and Comparison with Observations
AU: Nash, E
EM: enash1@san.rr.com
AF: UCSD, Dept. of ECE, MC 0407, La Jolla, CA 92093-0407 United States
AU: * Krauss-Varban, D
EM: varban@ece.ucsd.edu
AF: UCSD, Dept. of ECE, MC 0407, La Jolla, CA 92093-0407 United States
AU: Karimabadi, H
EM: homa@ece.ucsd.edu
AF: UCSD, Dept. of ECE, MC 0407, La Jolla, CA 92093-0407 United States
AU: Daughton, W
EM: daughton@lanl.gov
AF: Los Alamos National Laboratory, Plasma Physics Group X-1, Los Alamos, NM 87544 United States
AU: Pritchett, P
EM: pritchet@physics.ucla.edu
AF: UCLA, Dept. of Physics, Los Angeles, CA 90095-1547 United States
AB: The magnetotail current layer is subject to a variety of instabilities. One of these is the ion-ion kink mode, arising from the presence of two ion populations - the cold lobe ions and the current-carrying hot plasma sheet ions. We have used linear theory, 3D hybrid (fluid electron, kinetic ions), and full particle simulations to examine the properties of ion-ion kink mode. We find that this mode is primarily driven by a velocity shear arising from the presence of multiple ion populations. The instability saturates as a result of broadening of the current layer and reduction of the velocity shear. This instability, however, differs in important aspects from the standard Kelvin-Helmholtz instability (KHI). Its linear mode properties exhibit dependencies on the kinetic details of the secondary ion population and its nonlinear evolution is found to be significantly different from previous MHD and Hall MHD treatments of the instability as well as from the KHI. In particular, the usual formation of vortices and coalescence that occur for the Kelvin-Helmholtz instability are absent for the ion-ion kink mode. Recent Cluster observations of modulated and bifurcated current sheets are discussed within the context of the ion-ion kink mode. Hybrid simulations with open boundary conditions and using the parameters for this event demonstrate a very good agreement between the wavelength, period, and amplitude of the ion-ion kink mode and the observed wave-like disturbance. It is shown that the observed "bifurcated" current sheet can be explained in terms of a traveling kink mode in which the current layer has a single continuous displacement into both hemispheres.
DE: 2471 Plasma waves and instabilities
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2744 Magnetotail
DE: 7843 Numerical simulation studies
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting