Magetic Pulse Plasma Nozzle Solver - ProkopHapala/SimpleSimulationEngine GitHub Wiki
We can use the assumption that conductor with approx. infinite conductivity can perfectly shied all time-varying magnetic field (this assumption is correct if change of magnetic field is fast enough with respect to the decay of eddy-currents due to resistivity). The conductor (e.g. metallic sheet off the nozzle, as well as plasma sheet such as surface layer of the expanding plasma ball) will operate as Faraday cage.
In such case we can neglect the dynamics of magnetic field and consider just stationary boundary conditions that magnetic field $B$ behind the conductor stay unchanged. In order to fullfill this condition there is current induced in the conductor. This current will compensate (shield) the change of magnetic field behind the Faraday cage walls, but it will also induce additional field in the un-shiedlded area, which may be considerably enhanced. See picture.