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

Abstract

The dependence of the first stage H + plasmaspheric refilling density on various parameters is examined using a kinetic transport model. The first stage 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 first two factors are actually studying numerical influences of physical phenomena. That is, the method of including these processes in the calculation is varied to determine the importance of calculational rigor. The two processes of interest are self-collisional feedback and the ambipolar electric field. The third influencing factor to be examined is the effect of coexistent energetic populations of the refilling rate. It is found that the results greatly depend on the method of incorporating self-collisions into the model, as the scattering and loss processes of the low-energy proton population 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 distribution function. It is also found that the ambipolar electric field is the dominant force term, increasing the densities in the plasmasphere by accelerating the particles through the low-altitude scattering zone. The hot populations are found to have only a minor influence near the equatorial region, where 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.