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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. Plain Language Summary: 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. Key Points: Increase in solar wind dynamic pressure leads to increase in plasma and magnetic pressures in the magnetosphereLarger solar wind dynamic pressure make the plasma pressure more symmetric around the EarthObservations reveal a local magnetic pressure minimum located near a plasma pressure maximum around 11RE on the nightside [ABSTRACT FROM AUTHOR]

The Earth's magnetosphere is filled with a collisionless plasma that exhibits non‐Maxwellian particle distributions which are well described by Kappa functions. In contrast to the Maxwellian, the Kappa contains not only density and temperature but also the kappa index that allows us to characterize the energetic tails. In this study, we analyze the response of the ion and electron Kappa distributions, obtained by fitting ion and electron fluxes measured by the five THEMIS satellites, to changes of the solar wind dynamic pressure. It was found that the solar wind dynamic pressure strongly affects the values of the kappa index, and that its impact depends on the magnetic local time (MLT). In particular, there is a significant dawn‐dusk asymmetry for low PSW values which is enhanced in the night side. Further, we observe a narrow partial ring‐shaped structure at different azimuthal extension that divides the plasma into two clearly defined domains. The results obtained reflect the global reconfiguration of the magnetosphere caused by variations of the solar wind dynamic pressure. Kappa distribution parameters and their average values for different ranges of PSW and MLT are provided, which we believe will contribute as realistic inputs to the modeling of the magnetosphere. Plain Language Summary: The Kappa distribution function, which combines the Maxwellian‐type and the power‐law distributions, has been widely used in literature to describe particle populations in space and astrophysical plasmas. In such environments, ions and electrons rarely experience collisions and they are out of thermal equilibrium, which allows us to get insights into the mechanism of energy transfer in these plasmas. The goal is to investigate the roles of non‐thermal particle distributions, and their response to solar wind dynamic pressure in poorly collisional plasma environments such as the Earth magnetosphere. The availability of high cadence Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite data have enabled us to conduct this statistical analysis using THEMIS and OMNI database. Our findings confirm that the ion and electron kappa parameters exhibit distinct behaviors when subjected to the dynamic pressure exerted by the solar wind. Moreover, we find an interesting narrow partial ring shaped structure at different azimuthal extension exhibiting a local minimum for ion kappa parameters, and a local maximum for electron kappa parameters. Key Points: The behavior of Kappa distribution parameters in the Earth magnetosphere in response to the variation of the solar wind dynamic pressure is studiedThe solar wind dynamic pressure strongly influence ion and electron kappa indicesThe core energy (Ec) exhibits a significant dawn‐dusk asymmetry for ions and much weaker for electrons in various range of PSW [ABSTRACT FROM AUTHOR]

The Earth's magnetosphere is mainly a collisionless plasma system with non‐Maxwellian particle distributions, which are often fitted by the kappa function. While the Maxwell distribution function is described by two parameters (density and temperature), the kappa distribution function has three parameters: density, core energy, and the kappa index that characterizes the slope at high energies. In this study, we fitted an ion flux measured by the five Time History of Events and Macroscale Interactions during Substorms satellites in the Earth's magnetosphere during quiet geomagnetic conditions by a single kappa distribution function. The data were constrained to the following regions: from seven Earth Radii (7 RE) to the Earth's magnetopause at the dayside, and up to 20 RE for other magnetic local time sectors. The two‐dimensional spatial distribution of the fitted parameters and their radial dependencies were analyzed. Regions of high and low κ‐parameter are selected and their formation is discussed. Key Points: Ion spectra obtained from the Time History of Events and Macroscale Interactions during Substorms satellite mission near the equatorial plane are fitted by a kappa distribution functionDistribution of three fitting parameters (density, core energy, value of k characterizing the spectra slope at high energies) are obtainedRegion of increased k index at geocentric distances 8–10 RE is selected [ABSTRACT FROM AUTHOR]