Solar wind-driven magnetospheric current variability during 2013 storms: Ground and space observations

This study investigates the influence of solar wind dynamic pressure, particle density, and the Z-component of the interplanetary magnetic field (IMF Bz) variations on magnetospheric current systems during three major geomagnetic storms in 2013 (March 17, June 1, and July 6), using a comprehensive set of observations from RBSP-B, Cluster, and ground-based equatorial magnetometer stations (AAE, MBO, KOU, GUA). Each event is analyzed in terms of IMF conditions, solar wind pressure, auroral activity, ion injections, and current system responses. We find that a sharp southward turning of IMF Bz and enhanced dawn–dusk electric field (Ey) during storm onset trigger dayside magnetic reconnection, compress the magnetosphere, and initiate substorm activity. These processes result in intensified auroral electrojet (AE) activity and multiple ion injections into the inner magnetosphere, as observed by RBSP-B. The injections correspond with enhanced ion density (up to ∼ 2 cm -3 ) and plasma- β (up to ∼ 150 - 200) in the near-Earth plasma sheet, leading to a rapid buildup of the ring current and ring current energy (peaking at ∼ 5.5 × 10 15 J) and strong SYM-H depressions. All these developments contribute to the main phase of the storm and field-aligned current (FAC) enhancements (up to ± 0.3 μ A/m 2 ), together with dynamic reconfigurations of current systems in both the magnetotail and dayside regions. The coordinated analysis reveals a consistent temporal linkage between auroral activity, ring current intensification, and FAC dynamics, confirming the causal role of substorm expansions and solar wind forcing in magnetosphere–ionosphere coupling. Ground magnetic field data show corresponding H-component depressions (up to -150 nT) at dip-equatorial stations, capturing the storm-time ring current asymmetry and confirming inner magnetospheric pressure variations. These findings underscore the critical role of solar wind–driven processes in governing storm-time electrodynamics and demonstrate the value of multi-platform, multi-scale observations in decoding the coupled geospace response.