Relations of the energetic proton fluxes in the central plasma sheet with solar wind and geomagnetic activities

Abstract

AbstractIn this paper, using 9 years of Cluster data, we statistically investigate the relations of central plasma sheet energetic proton fluxes, ~30 keV to 380 keV, with the solar wind parameters and geomagnetic indexes. The energetic proton fluxes increase with increasing solar wind dynamical pressure and solar wind speed. The energetic proton fluxes are more correlated with solar wind dynamical pressure than with solar wind speed. During northward interplanetary magnetic field (IMF) Bz, energetic proton fluxes are independent of northward IMF Bz, while during southward IMF Bz, energetic proton fluxes are highly correlated with southward IMF Bz and increase with increasing |IMF Bz|. The response time of energetic proton flux to southward IMF Bz is between 40 and 100 min. The energetic proton fluxes are correlated with plasma sheet ion temperature. The energetic proton fluxes increase with increasing indexes of Kp, AE, and |Dst|. Among the three geomagnetic indexes, the central plasma sheet energetic proton fluxes are most correlated with Kp index with the largest correlation coefficient being 0.82. The energetic proton fluxes are large during positive Dst index, suggesting that the sharp increase of solar wind dynamical pressure can enhance the plasma sheet energetic proton fluxes. The enhanced plasma sheet energetic proton fluxes may be important for geomagnetic storms and substorms since they can possibly directly become the source of ring current and substorm‐injected energetic particles without the need of additional acceleration process in the inner magnetosphere.