HR: 1340h
AN: SM43C-1541    [Abstracts]
TI: Can kinetic plasma simulation and MHD talk to each other?
AU: * Brackbill, J U
EM: jerrybrackbill@comcast.net
AF: ParticleSolutions, 305 SE 41st Ave, Portland, OR 97214, United States
AU: Lapenta, G
EM: lapenta@lanl.gov
AF: LANL, T-15, Los Alamos, NM 87544, United States
AU: Lapenta, G
EM: lapenta@lanl.gov
AF: K U Leuven, Center for Plasma Astrophysics, Leuven, 3001, Belgium
AB: Kinetic simulations show faster tearing mode growth and higher amplitude saturation with electron temperature anisotropy. Implicit simulations in 3D show the lower-hybrid drift instability (LHDI) generates anisotropy and that spontaneous, small-scale tearing evolves into rapid, large-scale reconnection. These results for idealized problems on very small scales need to be tested on larger systems with more realistic boundary conditions, for which we need new methods. We extend implicit simulation to magnetohydrodynamic (MHD) scales by adding a simple but self-consistent collision model to Celeste. An input parameter switches Celeste from a kinetic simulation to Hall-MHD, and can be given different values in different regions so that MHD and kinetic regions interact, flux conservation conditions are rigorously satisfied, and the two plasma populations mix on ion time scales. In 2D, we simulate the LHDI with uniform collisionality, and it grows and saturates normally at low collision rates, but with reduced temperature anisotropy. We model a finite-width current sheet in the direction of current flow, as in the magnetotail, using adjacent collisional and collision-less regions. The resistance to current flow in the collisional region induces an out-of-plane return current flow in the collision-less region. To study embedding a kinetic region in a larger MHD domain, we introduce a collisional region along the magnetic field direction, which can cause localized reconnection unless done carefully. We characterize the transparency of the boundary between kinetic and MHD regions to the propagation of waves and plasma flow, and evaluate the adequacy of our simple collision model.
DE: 7829 Kinetic waves and instabilities
DE: 7833 Mathematical and numerical techniques (0500, 3200)
DE: 7835 Magnetic reconnection (2723, 7526)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting