HR: 0830h
AN: SH31A-1094    [PDF]
TI: Laboratory Observation of Fast Collisionless Reconnection$^*$
AU: * Egedal, J
EM: jegedal@psfc.mit.edu
AF: MIT,PSFC, 167 Albany St., Cambridge, MA 02139 United States
AU: Fox, W
EM: willfox@mit.edu
AF: MIT,PSFC, 167 Albany St., Cambridge, MA 02139 United States
AU: Porkolab, M
EM: porkolab@psfc.mit.edu
AF: MIT,PSFC, 167 Albany St., Cambridge, MA 02139 United States
AU: Fasoli, A
EM: ambrogio.fasoli@epfl.ch
AF: CRPP, EPFL, Lausanne, CH-1015 Switzerland
AB: Magnetic reconnection in the collisionless regime is studied on the Versatile Toroidal Facility (VTF). The detailed evolution of the profiles of plasma density, current density, and electrostatic potential at the onset of driven reconnection is reconstructed experimentally. Despite a constant, externally imposed reconnection drive, we show that the reconnection does not proceed in a steady-state manner. The formation and decay of the current is shown to be related to the evolution of the electrostatic potential and the associated ion polarization currents. The size of the diffusion region is inferred from the detailed knowledge of the electrostatic potential, and is shown to scale with the drift orbit width of the electrons insensitive to the ion mass and plasma density [1]. The accurate characterization of the steady state electric and magnetic field profiles provides an excellent basis for detailed kinetic simulations of the reconnection process. With the known electric and magnetic fields Liouville's equation is readily solved numerically providing the detailed phase space distribution function of the electrons. The current profiles, obtained from the first moment of the theoretical electron distribution function, are consistent with the measured current profile. Also consistent with VTF experiment results, the theoretical current densities are three orders of magnitude below the classical value, $E/\eta_s$. The phase space distributions of the electrons reveal non-Maxwellian features, which are fundamental in accounting for the momentum balance of the electrons in the vicinity of the X-line. The strong non-Maxwellian features also represent a source of free energy which can excite electromagnetic instabilities and fluctuations. [1] Egedal J, Fasoli A and Nazemi J, (2003) Phys. Rev. Lett. 90, 135003. $^*$ This work is supported by DOE and NSF
DE: 0600 ELECTROMAGNETICS
DE: 0654 Plasmas
DE: 2700 MAGNETOSPHERIC PHYSICS
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting