Solar wind transient currents: statistical properties and impact on Earth's magnetosphere

Solar wind discontinuities carry intense transient currents and significantly contribute to the turbulent spectrum and plasma heating. The most-investigated characteristics of these discontinuities are the magnetic field configuration and the current density, whereas plasma characteristics attract less attention. In this study, we utilize eight years of ARTEMIS spacecraft observations in the solar wind to investigate plasma density, velocity, and temperature variations across discontinuities. We also consider the role of discontinuities in the development of Earth's magnetospheric perturbations. We show that observed discontinuities can be separated into two groups: (i) discontinuities with weak plasma density variations and a significant correlation between the solar wind and Alfven velocities, (ii) discontinuities with significant variations of plasma density and temperature. For most discontinuities, observed density variations anti-correlate with temperature variations, but larger density/temperature variations correspond to stronger current densities. Time intervals characterized by increased occurrence rate of solar wind discontinuities correspond to enhanced geomagnetic activity in the Earth's magnetosphere as characterized by geomagnetic indices.