Angular Momentum Injection into a Penning-Malmberg Trap

It is demonstrated using conventional uid theory that angular momentum can be injected into a single component plasma con ned in a Penning-Malmberg trap via an externally generated, oscillating, non-axisymmetric, electric eld. The torque exerted on the plasma by the electric eld is a highly non-monotonic function of the plasma angular rotation velocity. The torque vs. angular velocity curve is dominated by sharp resonances at which the angular phase velocity of a particular poloidal harmonic of the external eld matches the plasma angular rotation velocity. The torque exerted on the plasma by a given poloidal harmonic is negative when the eld rotates faster than the plasma, and vice versa. This rather surprising behaviour is shown to be entirely consistent with a standard result in hydrodynamic theory, but is generally not observed in present day experiments.