Electron Hall, Electron Inertial, And Ion Dynamical Effects On The Magnetic Field Penetration Of Opening Switch Plasmas

The ANTIIM 1 simulation model has been used to examine the penetration of a B z magnetic field along the axial (x-) direction of a planar plasma opening switch (POS): 1) For the model situation in which the density profile as a function of y is constant from the cathode up lo Y b , then proportional to l/(y t + ε - y) and finally constant again from y t to the anode, we can expect non-linear shock penetration 2 of the magnetic field at a speed v w = -B/(2n o d) in the electron MID approximation, where the ions are taken as immobile. Here, B o (< 0) is the drive (piston) field at the generator edge of the plasma, n o , is the density from the cathode up to Y b , d = y t - Yb, and ε sets the density near the anode. Indeed, in simulation we observe a planar penetrating magnetic shock in the density ramp region, when the ion mass is artificially very large, the electron mass negligible, and when collisionality and the displacement current are suppressed. Current sheets now at both Y t and Y b · When the physical electron mass is employed, we find that the magnetic shock front is followed by a train of wavelets. These are broadened by the inclusion or the displacement current, and/or resistivity. 2) Examining the cathode physics we note that the conventional assumption that electrons are introduced at vanishing low velocity from a high density cathode plasma (Child-Langmuir emission) leads to anomalously deep magnetic penetration near the cathode, as electrons are accelerated up to the speeds associated with the classical skin depth. The advective reduction or the local electron velocity acts much like a large effective resistivity. 3) Finally, restoring the physical mass to the ions, we show that the magnetic pressure gradients from the current sheets along the electrodes and near the density toughs can steepen the density gradients, enhancing magnetic penetration ahead or the magnetic piston up to a distance the order of c/w pi . The talk will indicate how the llall, electron inertial and ion dynamical effects combine to determine the global opening dynamics of the planar POS.