A three-dimensional model of wire array instability, ablation, and jetting

A simplified algebraic model is set up to describe the principal features of the physics of wire array behavior in the early phases. Each wire is assumed to have evolved into a liquid-vapor core surrounded by a coronal plasma which carries most of the current. This plasma is unstable to m=0 instabilities, this instability being MHD or possibly electrothermal driven by inward radial heat flow on each wire. The joule heating occurs mainly in the necks of the sausage mode; flux limited heat flow transfers the energy to the core which erodes and ablates as a plasma at the sound speed. Free expansion at this velocity occurs into the lobes of the m=0 structure, and by rocket action the J_×B_ inward global force deflects the flow into inward precursor-jets. It is shown that the magnetic Reynolds´ number is less than one, and for a rapidly rising current results in negligible current or magnetic field in the precursor, as found usually in experiments. In addition, it is found that in the necks the Hall parameter is much less than one, consistent with the field-free model of flux limited heat flow.