Polarization reversal of Alfvén waves in a non-axisymmetric region of a quadrupole-anchored tandem mirror

Abstract

Mode-selective excitation of Alfv\'en waves is made by use of azimuthally rotating, radio-frequency antennas in the central cell of the GAMMA 10 tandem mirror. It is found that the wave polarization reverses from right handed in the central cell to left handed in the anchor cell and vice versa. Ions in the anchor cell are significantly heated by a fast wave excited in the central cell and not by a slow wave. The polarization reversal and the wave-mode-dependent ion heating are interpreted in terms of a linear mode conversion which is caused by a mode coupling between fast and slow Alfv\'en waves via a spatial modulation of the magnetic field in the quadrupole-field region.