Enhanced Resistivity in Strongly Non-Homogeneous Wire-Array Plasma

Summary form only given. Recent experimental data demonstrates that wire array loads (a) radiate more energy than could be coupled to them via change of inductance, and (b) start radiating before the main mass stagnates at the axis. This indicates that the wire array plasma operates as a resistive rather than inductive load. Wire array plasma had been observed to be very non-homogeneous prior to stagnation (radial flares, etc.). It is known that penetration of magnetic field into a strongly non-homogeneous medium with magnetized electrons, Omega_e tau_eGt1, is very different from classical diffusion into a conducting fluid, and resembles more of a percolation. At Omega _etau_eGt1 , which is ensured because the corona density is at least one order of magnitude less than the average plasma density, the magnetic field is advected by the electron flow along complicated trajectories, conserving the value of B/n_e=const. We propose a scaling law for effective resistivity of such plasma, assuming that the magnetic field is advected into the interior of the array along the low-density corona, of the observed plasma flares, as in the plasma of opening switches. The average electron displacement is Deltal=(j/en_e)Deltat. Assuming the flares to be random, and estimating Deltat as the diffusion time of magnetic field from the flare, Deltat~4pisigma a²/c², where a is the radius of the flare plasma and sigma is its Spitzer conductivity, we find that the effective conductivity is decreased by a factor of 1+h(Omega_etau_e)². We demonstrate how the dimensionless coefficient h that enters this scaling is determined by matching 1D rad-hydro simulation results to the experimental data obtained with W wire arrays on Z