Collisionless energy coupling to electrons by helicon waves in the near field of an antenna

Linear kinetic damping mechanisms of helicon waves in helicon wave driven plasma sources are re-examined. It is demonstrated that a reversal of the phase velocity of the wave in the near field of an antenna can lead to a transient overshoot in the rate of work done by the wave. This overshoot occurs when the magnitude of the phase velocity is a few times the thermal speed and Landau damping is the dominant kinetic absorption mechanism. These conditions often occur in low field and low density sources. The overshoot in the rate of work done by the wave may be an order of magnitude larger than the far-field Landau absorption rate. The effect of collisions is also assessed.