HR: 0800h
AN: SM51A-07    [Abstracts]
TI: Kinetic Simulations of Collisionless Reconnection in Pair Plasmas
AU: * Yin, L
EM: lyin@lanl.gov
AF: Los Alamos National Laboratory, MS-F699, Los Alamos, NM 87545, United States
AU: Daughton, W
EM: william-daughton@uiowa.edu
AF: University of Iowa, Department of Physics & Astronomy, 511 VAN, Iowa City, IA 52242, United States
AU: Bowers, K J
EM: kevin.j.bowers@ieee.org
AF: Los Alamos National Laboratory, MS-F699, Los Alamos, NM 87545, United States
AB: Despite a great deal of research effort, many basic issues regarding collisionless reconnection remain poorly understood. Although fully kinetic simulations offer a first principles approach, the large separation between electron and ion spatial and temporal scales has severally limited these computational studies. In contrast, the problem of magnetic reconnection in an electron-positron plasma is feasible in both 2D and 3D. It has been suggested that reconnection in pair plasmas may be of interest to certain astrophysical problems. Furthermore, this limit is useful to consider in the effort to understand the essential physics of magnetic reconnection, since there is no scale separation and it can be shown analytically that there are no whistler waves. In this work, we first examine the limit of large-scale 2D systems. Consistent with recent publications, it is demonstrated that reconnection rates remain fast for very large systems but a steady-state is never achieved. Instead the reconnection dynamics proceeds by the repeated formation of secondary islands as the diffusion region expands. From linear Vlasov theory, the unstable eigenmodes in a pair plasma include collisionless tearing and the drift-kink mode. In 3D simulations, the box length in the direction of the current can be selected to either permit or exclude the drift-kink. In the limit where the box length is short enough to exclude the drift-kink mode, reconnection proceeds essentially in the same manner as the 2D simulations. However, when the simulation box is long enough to allow the drift-kink mode, the reconnection dynamics change dramatically with complicated 3D structures resulting from the nonlinear interaction between collisionless tearing and drift-kink. These results may have some relevance to reconnection in hydrogen plasmas since the drift-kink mode is replaced by the ion-ion kink mode at high mass ratio.
DE: 7526 Magnetic reconnection (2723, 7835)
DE: 7835 Magnetic reconnection (2723, 7526)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly