The Middle and Low Latitude Ion Composition Variations Observed by the DMSP Satellites on 20-31 August 2018

The coupling between the ionosphere and plasmasphere is not known well during the quiet and storm times. The topside ionosphere ion composition reflects the exchange between the ionosphere and plasmasphere. We used the DMSP satellite observations to show the changes of the 840 km altitude H+ and O+ ions at similar to 3-6 LT in the mid- and low-latitudes on 20-31 August 2018 where a storm occurred on 25 August. The H+ was the main ion at 3-4 LT, and its concentration presented two peaks around 40 degrees N/S magnetic latitudes on 20-24 August. The H+ concentration strongly lessened for more than five days around 40 degrees N/S magnetic latitudes in the recovery phase of the storm on 26-30 August. Further, the enhancement and reduction of the H+ concentration persisted mainly in the Pacific and Asian sectors. The O+ density increased in Northern Hemisphere at 6:36 LT, and the H+ concentration showed the maximum around the magnetic equator during the quiet times, while the H+ concentration still mainly reduced around 40 degrees N/S and stronger at 40 degrees S in the recovery phase. The plasmaspheric total electron content showed a peak around the magnetic equator on 20-24 August, and the peak was weakened or disappeared on 26-30 August. The plasmasphere might be the principal sources for the mid-latitude H+ enhancement along the geomagnetic field lines during the quite times and the storm-time suppressed plasmasphere plasma density would weaken the supply of the H+ at 840 km altitude.