Three-dimensional electron magnetohydrodynamic reconnection. I. Fields, currents, and flows

Abstract

In a large laboratory plasma, reconnection of three-dimensional (3-D) magnetic fields is studied in the parameter regime of electron magnetohydrodynamics. A reversed magnetic field topology with two 3-D null points and a two-dimensional (2-D) null line is established, and its free relaxation is studied experimentally. Major new findings include the absence of tilting instabilities in an unbounded plasma, relaxation times fast compared to classical diffusion times, dominance of field line annihilation at the 2-D current sheet versus reconnection at 3-D null points, conversion of magnetic energy into electron thermal energy, and excitation of various microinstabilities. This first of four companion papers focuses on the magnetic field topology and dynamics.