HR: 1340h
AN: SM23B-0431    [Abstracts]
TI: Equilibrium Theory and Nonlinear Evolution of Bifurcated Current Sheets
AU: Matsui, T
EM: tatsuki-matsui@uiowa.edu
AF: Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242
AU: * Daughton, W
EM: william-daughton@uiowa.edu
AF: Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242
AB: The vast majority of simulations and linear theory for thin current layers have employed the well known Harris equilibrium for the initial condition. Although this is a convenient choice, the observed structure of current layers in the magnetosphere is considerably more complicated. In particular, satellite observations indicate the existence of bifurcated current sheets in the magnetotail. Furthermore, kinetic simulations initialized with a simple Harris equilibrium have been observed to quickly transition into a bifurcated structure (Daughton, Ricci and Lapenta, Phys. Rev. Lett 93, 105004, 2004) due to the nonlinear development of the lower-hybrid drift instability. Motivated by these developments, we employ a standard approach for constructing Vlasov equilibria (Camporeale and Lapenta, JGR 110, A07206, 2005 and Schindler and Birn, JGR 107, 1193, 2002) in order to develop a more realistic initial condition for kinetic simulations and linear stability analysis. A new expression for the functional form of the distribution function is chosen in manner to allow a great deal of flexibility in adjusting the equilibrium profiles. The model distribution function is a linear sum of a generalized Harris term and a Channel term. The merits of the model are: 1) It can generate realistic profiles of the current density bifurcation as well as other physical quantities in accordance with in-situ observations, 2) By the choice of the parameters, the expression can be easily transformed back to the standard Harris equilibrium. 3) Current profiles generated by the model can be adjusted to closely match the thin bifurcated structures observed in kinetic simulations ¹. This new Vlasov equilibrium has been implement as the initial condition in a 2D kinetic simulation code and initial results will be discussed.
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2744 Magnetotail
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005