Hybrid simulations of the cusp and dayside magnetosheath dynamics under \ quasi-radial interplanetary magnetic fields

Abstract: Under quasi-radial interplanetary magnetic fields (IMF), foreshock turbulence can have an impact on the magnetosheath and cusps depending on the location of the quasi-parallel shock. We perform three-dimensional simulations of Earth's dayside magnetosphere using the hybrid code HYPERS, and compare northward and southward quasi-radial IMF configurations. We study the magnetic field configuration, fluctuations in the magnetosheath and the plasma in the regions around the northern cusp. Under northward IMF with Earthward $B_x$, there is a time-varying plasma depletion layer immediately outside the northern cusp. In the southward IMF case, the impact of foreshock turbulence and high-speed jets, together with magnetopause reconnection, can lead to strong density enhancements in the cusp.