Plasma dynamics in microsecond megaampere plasma opening switches

The paper considers the transport of a magnetic field in highly ionized plasma of microsecond megaampere plasma opening switches. Self-similar solutions for plasma aggregation by a linearly increasing magnetic field are derived. For these solutions, the magnetic field energy in the current channel is much lower than the energy of the accelerated plasma flow. The effect of Joule heating of the plasma becomes profound only with a uniform current density. It is shown that the evolution of the magnetic field in the accelerated flow is reduced to diffusion with an effective electrical conductivity proportional to the harmonic average of the Spitzer conductivity and conductivity dependent on the magnetic field in the current channel. Thus, during about the first 100 ns of the current pulse the conductivity of the current channel increases due to the plasma heating and, as the plasma is accelerated, its conductivity decreases. (C) 2011 American Institute of Physics. [doi:10.1063/1.3649944]