Effects of various transport processes on the streaming ion density duringthe first stage of plasmaspheric refilling

The dependence of the first stage H+ plasmaspheric refilling density on var ious parameters is examined using a kinetic transport model. The first stag e of refilling is defined as the time for the source cone to reach a quasi- steady-state level. Three influencing factors are examined in detail. The f irst two factors are actually studying numerical influences of physical phe nomena. That is, the method of including these processes in the calculation is varied to determine the importance of calculational rigor. The two proc esses of interest are self-collisional feedback and the ambipolar electric field. The third influencing factor to be examined is the effect of coexist ent energetic populations of the refilling rate. It is found that the resul ts greatly depend on the method of incorporating self-collisions into the m odel, as the scattering and loss processes of the low-energy proton populat ion interacting with itself has a significant influence on the early stage density. This interaction is particularly strong in the low-altitude region where the densities are high enough to substantially alter the distributio n function. It is also found that the ambipolar electric field is the domin ant force term, increasing the densities in the plasmasphere by acceleratin g the particles through the low-altitude scattering zone. The hot populatio ns are found to have only a minor influence near the equatorial region, whe re they slow the H+ streams down and cause the density to slightly increase . The effects of hot ions are more pronounced in the streaming velocity and the temperature anistropy, but still confined to the equatorial region. (C ) 2000 Elsevier Science Ltd. All rights reserved.