HR: 1330h
AN: SM52B-0587    [PDF]
TI: Electron Inertia Effects in Highly Rolled-up MHD-Scale Kelvin-Helmholtz Vortices
AU: * Nakamura, T
EM: takuma@geo.titech.ac.jp
AF: Department of Earth and Planetary Sciences Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan, Tokyo, 152-8551 Japan
AU: Fujimoto, M
EM: fujimoto@geo.titech.ac.jp
AF: Department of Earth and Planetary Sciences Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan, Tokyo, 152-8551 Japan
AB: In order to understand the universality of substantial non-MHD effects in MHD-scale Kelvin-Helmholtz (KH) vortices, we have performed two-dimensional simulations by a two-fluid system including finite electron inertia effects. An MHD-scale velocity shear with density gradient between two regions is set up and evolution of MHD-scale KH-mode is followed. Firstly, the magnetic field is assumed to be perpendicular to the flow and the simulation plane. In this case, we have already shown the quick decay of an MHD-scale KH vortex induced by the electron effects to exist; smaller vortices appearing within the MHD-scale vortex grow in size as they intrude into the center of the parent_fs vortex. Then the well-ordered parent_fs flow pattern is destroyed. By investigating the detailed nature of the decay process, here we show that the parameter range for the quick decay involves the typical parameter range of the tail-LLBL and thus the vortex decay is well expected in the tail boundary layer. Secondly, we have simulated cases with in-the-plane magnetic field component. We particularly focus on the case where magnetic field lines on both sides of the shear layer are parallel to each other. In this case, the magnetic reconnections within the MHD-scale vortex are generated by the electron inertia effects when the vortex highly rolls-up, stretching the field lines into an anti-parallel geometry overcoming the tension of in-the-plane magnetic field. The number of the magnetic islands formed by reconnection and the degree of the electron acceleration in the islands depend on the size of the vortex measured by the electron inertial length. Furthermore, when in-the-plane magnetic intensity is extremely different between the two sides of the shear layer, we observe the magnetic islands to be injected into the side with the weaker field. We will present more details pointing to the general importance of the electron effects in an MHD-scale KH vortex and discuss its relevance to dynamics of the tail-LLBL.
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2748 Magnetotail boundary layers
DE: 2772 Plasma waves and instabilities
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting