Connecting the Geoelectric Field to its Magnetospheric Sources in a Global Hybrid-Vlasov Simulation

Field-aligned currents originating in Earth's magnetosphere can flow down to the ionosphere, where they spread out horizontally in order to close the circuit. These currents produce a fluctuating magnetic field, which in turn induces the ground geoelectric field. We study this system using the 3D global hybrid-Vlasov code Vlasiator, which has recently been extended to model ionospheric physics. This approach allows a straightforward analysis of how induced fields on Earth's surface are connected to their magnetospheric drivers. In particular, we consider how fluctuations near Earth's magnetopause can ultimately give rise to a dayside geoelectric field. Possible driving mechanisms considered include flux transfer events and magnetopause surface waves.