Study Of Interplanetary Condition Effect On Geomagnetic Pulsations And Ionosphere-plasmasphere Response

A complex coupling system is formed by the solar wind, magnetosphere and ionosphere in geospace. And an important process in geospace that is still not fully understood is the plasma transport between the plasmasphere and the ionosphere during different interplanetary disturbance and geomagnetic condition. Additionally, the response of the periodic disturbance of the geomagnetic field, for example, geomagnetic pulsation and ECS, to the interplanetary disturbance, is paid attention on studying the problem in space weather. In the paper, we use the observation data of Chinese Meridian Project and OMNI database by satellites and global3-D MHD model to answer above two mentioned questions.1、Transport process of the plasmasphere and ionosphereFirstly, using the method of remote sensing magnetosphere using ground-based observations of ULF waves, combined with the dipole magnetic field model and plasma density model, we analysis statistically the changing of simultaneous observations of the plasmaspheric and ionospheric densities during five moderate magnetic storms. The observations show that the plasmaspheric density drops significantly more than the prestorm value. The ionospheric electron density reductions take place before the plasmaspheric density reaches its minimum. These findings suggest that the plasmaspheric depletion is very likely due to the reduced plasma supply from the ionosphere. Therefore, the plasmasphere dynamics seems to be controlled by the ionosphere during magnetic storms.Secondly, besides magnetic storms, we study the changing of the plasmaspheric and ionospheric densities in response to solar wind dynamic pressure pulsation during the geomagnetic quite period. The result suggests the plasmasphere in response to the solar wind dynamic pressure pulsation shows a significant depletion. However, the ionospheric electron density first increases and then decreases to the origin level, which is opposite to the behavior during magnetic storms. Preliminary analysis shows that the plasmaspheric depletion may be mainly caused by the interplanetary southward magnetic field and changing dawn-dusk electric field. The plasmaspheric density variations seem to be controlled by both the IMF and ionospheric conditions.2、The response of the periodic disturbance of the geomagnetic field to interplanetary conditionWe study the periodic perturbation of the geomagnetic field in response to the interplanetary disturbance from observation and numerical simulation. The geomagnetic pulsation is defined as the short periodic geomagnetic disturbance.We analysis the source and the characteristics of Pc3-4geomagnetic pulsation in spatial and temporal distribution. Preliminary results show there is the significant dawn-dusk asymmetric distribution of the Pc3-4geomagnetic pulsations in the middle-low latitudes, with Pc3-4pulsations activity observed mainly in the pre-noon sector, during both time periods. They are closely related to the interplanetary conditions, with high-speed solar wind leading to the enhancement of the Pc3-4geomagnetic pulsations. However, Pc3-4pulsations activity is not observed near the equatorial low latitudes due to latitudinal effect.Additionally, interplanetary (IP) shocks could affect the geomagnetic field by changing the current systems in the magnetosphere-ionosphere region. Equivalent current systems (ECS) are defined as a simply proxy for the temporal and spatial evolution of the large-scale complex geomagnetic perturbation that it is assumed to be caused by the current in the thin ionosphere layer. We utilize the global3-D MHD model to analysis the instantaneous response of the ionospheric ECS to interplanetary shock. The simulation results suggest ECS images gradually evolve to the shock downstream images by control of the interplanetary condition, which is relevant to the interplanetary shock intensity.