The effect of axial temperature profile on the thermal instability in high current-carrying plasmas

Current-carrying plasmas exhibit strong temperature gradients in the proximity of bounding electrodes. A modal analysis of the thermal instability shows that a constriction always starts near the electrodes. It is localized there, where the temperature dependence of the thermal and electrical conductivities are assigned parameter values that are characteristic of plasmas in magnetohydrodynamic channels. In the case of practically full ionization and very large pressures, that prevail in arc-driven railguns, the constriction expands axially over the entire length of the discharge.