Skin current driven microinstabilities in a magnetized plasma.

Currents flowing parallel to a magnetic field with a gradient in the perpendicular direction are present in many interesting situations in plasma physics. In Ohmic heated experiments the current gradient is accompanied by a temperature gradient, and it is shown that both gradients can drive unstable, low-frequency, localized modes. These modes are studied using various models for the electron and ion dynamics (including an integral formalism that retains finite ion gyroradius effects) and considering the effects of density gradients and collisions. A detailed numerical study of the parametric dependence of the mode frequency and structure and a mechanism for anomalous current penetration are presented. [ABSTRACT FROM AUTHOR]