The Response of the Earth Magnetosphere to Changes in the Solar Wind Dynamic Pressure: 1. Plasma and Magnetic Pressures

In the present study, the influence of the solar wind dynamic pressure on the plasma and magnetic pressures of the magnetosphere is studied. We use 11-year Time History of Events and Macroscale Interactions during Substorms (THEMIS) instruments for plasma and magnetic field measurements in the magnetosphere and the OMNI database for solar wind dynamic pressure and IMF data. We focus on the effects of the solar wind dynamic pressure (PSW) and consider only times in which the interplanetary magnetic field (IMF) components are within +/- 5 nT. We find that the plasma pressure inside the magnetosphere follows the solar wind dynamic pressure and that an increase in PSW also influence the day-night pressure asymmetry. Our analysis also reveals the existence of ion and electron drifts from midnight toward the dusk and dawn sectors, respectively. We observe a local magnetic pressure minimum located near a plasma pressure maximum at around 11 RE on the nightside. Comparing the effect of PSW on both plasma and magnetic pressures, we observe trends which are consistent with the diamagnetic properties of plasmas. In general, the distribution of plasma pressure within the Earth's magnetosphere is an important criterion for evaluating the magnetostatic equilibrium and electric current system. The outcome of this study should provide additional methodologies for the characterization of key plasma characteristics within the magnetosphere. Magnetospheric activity and space weather are driven by the interaction of the solar wind and the Earth's magnetic field. The solar wind dynamic pressure and interplanetary magnetic field (IMF) are two important factors that affect the behavior of the Earth's magnetosphere. The interaction between these two factors are complex and can have significant effects on our planet. Based on 11-year plasma and magnetic field measurements, obtained from THEMIS satellites, we investigated the effect of solar wind dynamic pressure on the plasma and magnetic pressures within the Earth magnetosphere. In this study, we show that changes in the plasma pressure within the magnetosphere are linked to variations in the solar wind dynamic pressure. Our findings confirm that the plasma pressure inside the magnetosphere is mainly controlled by the solar wind dynamic pressure, which can be attributed to pressure balance. Overall, the distribution of plasma pressure within the Earth's magnetosphere is a key parameter for evaluating the magnetostatic equilibrium and electric current system. Our results are expected to offer scientists additional methodologies for characterizing main plasma parameters in the magnetosphere. Increase in solar wind dynamic pressure leads to increase in plasma and magnetic pressures in the magnetosphere Larger solar wind dynamic pressure make the plasma pressure more symmetric around the Earth Observations reveal a local magnetic pressure minimum located near a plasma pressure maximum around 11RE on the nightside