Wave-particle interactions between the ring current particles and micropulsations associated with the plasmapause

In this paper the drift-wave instabilities likely to occur at and near the plasmapause during the period of magnetospheric disturbances are described. The analysis predicts that the proton cyclotron drift loss-cone wave (non-flute electrostatic mode) grows at and near the plasmapause through the drift cyclotron resonant interactions of the ring current protons. The wave is particularly effective for the turbulent loss of the ring current protons just beyond the plasmapause. In a region just inside the plasmapause, the wave is likely to be stabilized by the Landau interaction of the plasmaspheric particles. The unstable wave propagates in opposite directions inside and outside the plasmapause. Accordingly, the proton precipitation pattern would be different in respective regions. The unified loss mechanism of the ring current protons is presented.It is suggested that an ordinary mode instability occurs through the drift resonant interactions with the ring current electrons far beyond the plasmapause. This wave is excited only in a high- plasma with the conditions that the electron temperature perpendicular to the magnetic field is greater than the parallel temperature and that the temperature gradient has an opposite sign to that of the number density and magnetic field. The frequency and wavelength of the fastest growing wave depend sharply on the temperature anisotropy as well as the strength of the inhomogeneities (in temperature, magnetic field and number density). The fastest growing wave has a period of 36.9 s under certain conditions. This wave is likely to be an origin of the pitch-angle diffusion of the ring current electrons.