Theory of gradient drift instabilities in low-temperature, partially magnetised plasmas

A fluid dispersion theory in partially magnetised plasmas is analysed to examine the conditions under which large-wavelength modes develop Penning-type configurations, that is, where an electric field imposed perpendicular a homogeneous magnetic field. The relation assuming slab geometry shows two types of low-frequency, gradient drift instabilities occur direction $\boldsymbol {E} \times \boldsymbol {B}$ and diamagnetic drifts. One type instability, observed when equilibrium plasma density are same direction, similar classic modified Simon–Hoh instability. second instability found for (i) opposite (ii) magnitude sufficiently larger than electron thermal speed. present suggests rotating spokes driven by such propagate as drift, can be or depending on conditions. This finding may account observation, some devices, rotation large-scale structures both $-\boldsymbol directions.