Laboratory experiments on magnetic reconnection in EMHD plasmas

Reiner Stenzel, Manuel Urrutia and Kyle Strohmaier

Experiments on magnetic field topologies with null points have been 
performed in a large laboratory plasmas. In particular, the relaxation of a 
field-reversed configuration (FRC) is studied in a plasma with magnetized 
electrons and unmagnetized ions (EMHD). Detailed measurements of the 
three-dimensional field topology in space and time will be presented. The 
relaxation process involves magnetic energy conversion into electron heat 
via field line annihilation in a toroidal current sheet. The rate is 
controlled by anomalous resistivity caused by current-driven ion sound 
turbulence. Tilting of the toroidal current layer is also observed and 
studied. It modifies the field topology by destroying the closed separatrix 
surface, leaving two radial and two spiral null points. Along open field 
lines propagating whistler vortices convect some of the stored field 
energy. Finally, the interaction between two FRCs is also studied. Their 
fields merge and shed vortices. Such interactions may occur in 3D whistler 
turbulence which is still poorly understood yet important in many neutral 
sheets.