Twostream modeling of plasmaspheric refilling

Plasmaspheric refilling on an L = 4 flux tube was studied by using a time-dePendent, hydrodynamic plasmaspheric flow model in which the ion streams from the tWO hemispheres are treated as distinct fluids. In the model the continuity, momentum, and energy equations of a twoion (O + and H+), quasi-neu.tral, currentless plasma are solved along aclosed geomagnetic field line; diffusive quilibrium isnot assumed. Collisions between all stream pairs and with neutral species are included. The model includes acorotating, tilted dipole magnetic field and neutral winds. Ionospheric sources and sinks are accounted for in a self-consistent manner. Electrons are assumed to be heated by ph0toelectrons. The model flux tube extends from 200-km altitude in one hemisphere to 200-km altitude inthe other hemisphere. Initially, the upwelling streams pass through each other practically un'unpeded. When the streams approach t e boundary inthe conjugate ionosphere, a shock develops there; which moves upward and dissipates slowly; at about the same time a reverse shock develops inthe hemisphere of origin, which moves Upward. After about 1 hour, large shocks develop in each stream near the equator; these shocks move toward the equator and downward after erossing the equator. However, these shocks are probably artificial, because counterstreaming flowsoccur in •each H + fluid, which the model can only handle by creating Shocks.