The observation of trapped ions in the equatorial region of the outer plasmaspheric flux tubes suggests interesting plasma processes, which can significantly affect the refilling of such tubes after geomagnetic storms. The trapped ions are created by perpendicular ion heating by wave-particle interactions. During the early stage of the refilling, the heated ions come from the field-aligned flows of thermal plasma from the conjugate ionospheres. If the heating is sufficiently strong, the mirror force on the heated ion decouples the interhemispheric plasma exchange, and each hemisphere refills with the plasma supplied by its own ionosphere. The generation of the trapped ions and the refilling processes are modeled by solving time-dependent plasma transport equations.

The refilling is found to occur in two stages. The first (initial) stage involves (1) development of supersonic flows from the conjugate ionospheres, (2) perpendicular ion heating at the equator, (3) retardation of the interhemispheric flow by the mirror force as the heated ions tend to flow downward from the equator, and (4) formation of shocks in the supersonic flows at the equator and their downward propagation to the conjugate ionospheres. This entire phase lasts only a few hours. Since shock formation in a hydrodynamic model is questionable, it is verified kinetically by means of a numerical simulation which shows that shocks form at the mirror points of the equatorially heated ions. The kinetic simulation deals with small-scale counterstreaming plasma expansion in a mirror type of magnetic field with minimum magnetic field at the center. The second stage of refilling starts when the temperature anisotropy created by the passage of the shocks begins to relax as a result of Coulomb collisions at relatively high latitudes where plasma density is relatively high. During this stage the flow from the conjugate ionospheres is generally subsonic, and the associated refilling is relatively slow. During the course of refilling in this subsonic stage, density and temperature in the flux tube evolve through a variety of structures.

The temperature anisotropy T⊥>T∥ is found to persist in an extended equatorial region over several days, but near the equator itself an approximate temperature isotropy (T⊥~T∥) is achieved in about a day after the start of refilling. When equatorial isotropy is achieved, the perpendicular temperature shows a double-peak structure with a peak on either side of the equator lasting over several days. ¿ American Geophysical Union 1992