Magnetospheric convection and the effects of wave-particle interaction on the plasma temperature anisotropy in the equatorial plasmasphere

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It is well known that in periods of increased geomagnetic activity as well as during geomagnetic storms the ring current penetrates into the plasmasphere. When hot anisotropic protons of the ring current penetrate a rather dense cold plasmasphere, the ion-cyclotron instability leads to the generation of MHD waves. Collisionless damping of these waves in the outer plasmasphere leads to its heating, and a maximum heating rate is observed in the geomagnetic equatorial plane. On the basis of the numerical solution of the equations of anisotropic hydrodynamics, the influence of the ring current on the thermal regime of the equatorial plasmasphere is investigated. The equations are integrated along plasma trajectories in the geomagnetic equatorial plane. The dependence of the plasma temperature and its anisotropy on the density variations along the drift trajectories and on the local time are analyzed for different ring current and plasmasphere parameters. The calculations show that the ion temperature exceeds the electron temperature by a factor of 1.5–2.0 and that ion temperature anisotropy can reach significant values in the evening sector.