Interhemispheric flow of thermal plasma in a closed magnetic flux tube at mid-latitudes under sunspot minimum conditions

Abstract

The coupled H + and O + time-dependent continuity and momentum equations are solved within a region of the L = 3 magnetic flux tube lying between (and including) the F2-layers of conjugate hemispheres. The method of solution is an extended and modified version of the Murphy et al. (1976) method. The model is used to study the coupling between the F2-layers of conjugate hemispheres during magnetically quiet periods. The results of the calculations strongly indicate that the protonosphere acts as a reservoir, with variable H + content, which prevents direct coupling between the F2-layers of conjugate hemispheres. However there is generally a significant interhemispheric flow of plasma. This flow is caused by conditions in the summer and winter topside ionospheres and it maintains continuity in the plasma concentration within the protonosphere. There are times when the direction of flow is from the winter hemisphere to the summer hemisphere. It is suggested that maintenance of the winter F2-layer at night is not assisted directly by the F2-layer of the conjugate summer hemisphere. It is shown that during the first few days of protonosphere replenishment after a magnetic storm there is an upflow of H + in the topside ionosphere at all times in the summer hemisphere. There is also an upflow of H + during the daytime in both hemispheres. A comparison with the results obtained when the interhemispheric H + flux is held permanently at zero shows that both F2-layers are little affected by the interhemispheric H + flux. Nevertheless both F2-layers are affected by the H + tube content of the protonosphere. When the H + flux at 1000 km in one hemisphere is much greater than the H + flux at 1000 km in the conjugate hemisphere, there is a corresponding signature in the interhemispheric H + flux. The results suggest that there is insufficient time between magnetic storms for complete replenishment of the protonosphere to occur.