DRIFT WAVE INSTABILITY IN MODEL OF A PERIODIC SLAB

The usual two-dimensional slab model with its magnetic field modulated by a small periodic part has been used to examine properties of the drift modes in the plasma of an average magnetic well e.g. multipole. There is no shear or rotational transform. The aim is a detailed examination of the effects caused by mirroring of the resonant electrons. It is found that a class of standing modes exists, out of which the mode with largest growth rate is an odd mode with wavelength double the connection length. The value of the growth rate of this mode, which concentrates in the high-field regions, is given in the limit of strong electron mirroring.