49th Annual Meeting of the Division of Plasma Physics
Volume 52, Number 11
Monday–Friday, November 12–16, 2007;
Orlando, Florida
Session DI2: Reconnection, Gamma-Ray Bursts, and Angular Momentum Transport
3:00 PM–5:00 PM,
Monday, November 12, 2007
Rosen Centre Hotel
Room: Salon 3/4
Chair: David Newman, University of Colorado
Abstract ID: BAPS.2007.DPP.DI2.1
Abstract: DI2.00001 : Towards a New Understanding of Collisionless Magnetic Reconnection
3:00 PM–3:30 PM
Preview Abstract
Abstract
Author:
William Daughton
(Los Alamos National Laboratory)
A central cornerstone of modern concepts regarding fast magnetic reconnection has
been the expectation that the non-ideal electron region remains localized on the
electron scale. Based on this understanding, it has been widely argued that the
reconnection rate is controlled by the ions in a manner that is insensitive to the
specific details of the electron physics. This picture implies that a single x-line will
lead to steady reconnection with an open geometry similar to the Petscheck model.
These expectations were largely based on two-fluid simulations and small-scale
kinetic simulations with periodic boundary conditions. Recently, this problem was
re-examined using 2D fully kinetic simulations with open boundary conditions
\footnote{Daughton, Scudder and Karimabadi, {\it Phys.~Plasmas} {\bf 13},
072101,2006} as well as the largest periodic simulations ever considered. In
contrast to previous expectations, both of these approaches demonstrate that the
length of the electron diffusion region expands in time to form a highly elongated
current layer with a width on the electron scale but a length that can exceed tens of
ion inertial lengths. These non-ideal electron layers exhibit multiple scales in the
outflow direction\footnote{Karimabadi, Daughton and Scudder, {\it
Geophys.~Res.~Lett.} {\bf 34}, L13104, 2007} with an inner region characterized by
strong out-of-plane current and an outer region marked by a collimated electron
jet. The formation of these highly elongated layers involves a competition between
the outward convection of magnetic flux with the non-ideal terms arising from the
divergence of the electron pressure tensor. Although it is possible to setup a
balance over limited durations, the resulting layers are always highly elongated.
Over longer time scales, these layers are unstable to the formation of secondary
magnetic islands leading to a reconnection process that is inherently
time-dependent. These results point to a very different picture regarding the
essential
physics of reconnection since both the reconnection rate and time dependence are
sensitive to the details of the electron physics.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.DPP.DI2.1