Influence of bounce resonances on excitation of Alfvén waves beyond the plasmasphere.

The stability of Alfven oscillations in the hot plasma located in the curvilinear geomagnetic field is considered. A general expression for the Alfven-instability increment is obtained, and the value of the increment is calculated numerically for the case of a parabolic magnetic field and a disturbance with an arbitrarily small wavelength that is of the order of the bounce frequency of particles oscillating between reflection points. The frequency dependence of the instability increment in the presence of bounce resonances is examined. Experimental data concerning Pi1c pulsations are interpreted on the basis of this frequency dependence.