Mechanisms of gradient-drift instabilities in partially magnetized ExB plasmas.*

Partially magnetized plasmas with magnetized drifting electrons in crossed electric (E) and magnetic (B) fields, and unmagnetized ions, are widely used in various applications, including space propulsion and material processing, and also occur in nature, such as the ionosphere. Such plasmas are typically the subject of gradient-drift instabilities driven by density, temperature, and magnetic field gradients. Negative energy mode instabilities may also be triggered by dissipation, e.g., collisions. In this work, we review some specific mechanisms of gradient-drift instabilities, including the effects of electron inertia, finite electron Larmor radius, and ion motion. It is shown that predictions of the fluid theory based on the low-frequency (ω<ω_ce) reduction of the general moment equations agree well with kinetic results.