Three-dimensional kinetic effects in SSX

M. R. Brown, C. D. Cothran, W. H. Matthaeus

We report several new results from spheromak merging studies at SSX 
with relevance to astrophysical reconnection and particle 
acceleration.  First, we report the measurement of non-ideal terms of 
the generalized Ohm's law at a reconnection site of a weakly 
collisional laboratory plasma.  Time resolved vector magnetic field 
measurements on a 3D lattice enables evaluation of the various terms. 
Results show that the Hall term dominates; resistive and electron 
inertia terms are small.  We suggest that electron pressure supports 
the reconnection electric field at the neutral point.  Second, we 
report experimental measurement of the in-plane Lorentz force and 
out-of-plane magnetic field associated with the Hall electric field 
near the reconnection zone.  Both show a quadrupolar structure at the 
ion inertial scale.  Earlier work at SSX has shown that formation of 
three-dimensional structure at the ion inertial scale is temporally 
and spatially correlated with the observation of superthermal, 
super-Alfvenic ions ions accelerated along the X-line normal to the 
local 2D plane of reconnection.  Anomalous resistivity, while not 
ruled out, is not required to account for the results.