Theory of an Electric-Current-Carrying Discontinuity Driven through Nonconducting Gas by a Lorentz Force

摘要

A physical model is presented for the structure of an electric-current-carrying discontinuity moving into nonconducting gas and leaving nonconducting gas behind. The model assumes a normal shock wave followed by a porous current sheet. A three-fluid analysis (electrons, neutrals, and singly-charged ions) is made for the case where the component of magnetic field normal to the plane of the discontinuity is zero. All the dependent variables can be computed as functions of displacement in the streamwise direction, as demonstrated in two specific examples. The model admits finite-strength current sheets as solutions, with the electron and ion density diminishing to zero upstream and downstream of the sheet. As seen moving with the discontinuity, the impressed electric field and the induced electric field are additive. This is in contrast to the case for magnetohydrodynamic shock waves, where these two fields cancel on both sides; and to gas-ionizing shock waves, where the two fields cancel on the downstream side. In the frame of reference moving with the discontinuity, the discontinuity dissipates electrical energy and decelerates the gas. (Author)