ABSTRACT
The nature of the instabilities depends critically on the interplay between the magnetic field and the spatial inhomogeneities. In many cases, the effects of force fields upon the motion of charged particles may also have to be taken into consideration. These force fields or inhomogeneities acting together with the magnetic field then produce various drift motions of charged particles. As in the cases of instabilities in homogeneous plasmas, such particle drifts play a very essential part in the interpretation and understanding of various instabilities in inhomogeneous plasmas. This chapter describes the drift motion that is most closley related to the instabilities in inhomogeneous plasmas. The collective properties of inhomogeneous plasmas are substantially modified from those of homogeneous plasmas. An especially remarkable feature is the appearance of the drift wave and the associated instability.
