A new laboratory experiment on magnetic reconnection

Abstract

In a large laboratory plasma reconnection of three-dimensional (3-D) magnetic fields is studied in the parameter regime of electron magnetohydrodynamics (EMHD). A reversed-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 that are 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. The experiment implies that EMHD processes near absolute magnetic null points must be considered in the multiscale physics of magnetic reconnection.