The high-altitude polar wind: Simulation and observation.

摘要

In comparing the transport and semikinetic descriptions of the expansion of the polar wind, it is found that the transport model produces shocks in the profiles of all moments, while a generalized semikinetic (GSK) model produces smooth profiles. The inadequacy of the transport model to deal with velocity dispersion, phase mixing and multiple-streams is clearly demonstrated. In the study of the effects of hot magnetospheric electrons on polar outflow, it is found that by imposing a large increase in electron temperature (T{dollar}sb{lcub}rm e{rcub}{dollar}) over a short altitude range, a potential barrier is formed at which H{dollar}sp+{dollar} is partially reflected. For cases in which the T{dollar}sb{lcub}rm e{rcub}{dollar} profile is established by thermal conduction from a high upper boundary T{dollar}sb{lcub}rm e{rcub}{dollar}, the upward flux of H{dollar}sp+{dollar} decreases with increasing upper boundary T{dollar}sb{lcub}rm e{rcub}{dollar}, while O{dollar}sp+{dollar} shows a peak in the upward flux. The polar cap O{dollar}sp+{dollar} data collected by the DE1/RIMS are analyzed by fitting drifting Maxwellian distributions to the retarding potential curves, so that the O{dollar}sp+{dollar} characteristics in terms of its density, velocity and temperature are determined. The results show that these observed data can be matched by the GSK model which includes the effect of centrifugal acceleration due to E {dollar}times{dollar} B convection. The model results also match other observed low- and mid-altitude polar wind density profiles. The matching with satellite data is obtained by using the GSK model which uses observed low-altitude O{dollar}sp+{dollar} polar wind data as lower boundary conditions. Model polar wind density profiles that match mid-altitude satellite data, as well as the newly analyzed O{dollar}sp+{dollar} velocity and temperature, can be obtained when an electron temperature and base ion temperature of 9000 K and an ionospheric convection electric field of 70 mV/m are assumed.