Measurements of Hall Reconnection in MST

Previous measurements in MST have established that two-fluid Hall effects produce a dynamo EMF during magnetic relaxation events (sawteeth), and therefore two-fluid dynamics are important to the macroscopic effects of reconnection. This Hall dynamo was established by measuring the nonlinear Hall term $(\tilde{J} \times \tilde{B})$ in the axisymmetric (flux-surface-averaged) Ohm's Law. Here, we report measurements of terms in the \em non\em-axisymmetric Ohm's Law, including the reconnection electric field and terms that balance this field. This analysis is applied to tearing modes with poloidal mode number $m=0$ and toroidal mode number $n\ge 1$. Measurements are performed with probes in the vicinity of the resonant surface, and clearly indicate that single fluid physics is not sufficient to explain this reconnection. In particular, nonlinear three-wave interaction Hall terms are a strong contributor to the dynamics of this reconnection and the associated island formation.