Low-frequency waves in a weakly ionized, rotating magnetoplasma

A single-fluid theory is developed which explains the experimental behavior of a low-frequency (∼ 2 kHz) flute instability in a hollow cathode discharge plasma. The effects of density gradient, centrifugal, and Coriolis forces due to plasma rotation in a nonuniform, radial electric field, and ion-neutral collisions are included in a linear fluid theory. A cubic dispersion equation results which is solved numerically using experimental plasma profiles. In the low-frequency limit (ω/Ωi ≪ 1), the dispersion relation reduces to a quadratic expression which is consistent with earlier work in the appropriate limits. Collisions are found to be stabilizing, while the Coriolis effect depends on the direction of plasma rotation. The theory is able to predict, within experimental uncertainty, the frequencies observed in two similar experiments.