The effect of externally applied oscillating electric fields on the l=1 and l=2 diocotron modes in non-neutral plasmas

A high-frequency oscillating electric field can change the properties of diocotron modes in non-neutral plasmas. The effect depends crucially on the azimuthal mode number, m, of the applied field. For m=0,±1 there is no effect, and for applied standing waves there is also no effect. But if the applied field has the form of a traveling wave with ‖m‖≥2, the frequency of stable diocotron modes can be modified and for ‖m‖≥3, the l=2 instability of hollow density profiles can be stabilized. The analytic results are verified with a nonlinear fluid simulation of an infinitely long non-neutral plasma.