SMALL-SCALE PLASMA INSTABILITIES IN NONUNIFORM CROSSED FIELDS.

A theory is derived for the electrostatic electron cyclotron and ion-acoustic instabilities which occur in a very inhomogeneous plasma with beta approximately equals 1 in crossed electric and magnetic fields (the thickness of the plasma slab is smaller than the ion gyroradius and larger than the electron gyroradius). The characteristic values of the wave growth rates are of order the lower hybrid frequency. It is found that the local approximation cannot be used for the electron cyclotron instability. A nonlocal equation is derived for the field of these waves.