Revealing Magnetosphere Feedback on Solar Wind - Magnetosphere Coupling via Numerical Experiment

Solar wind - magnetosphere coupling is a core element of space weather and magnetospheric physics. While it is generally understood that this coupling process is complex and involves effects from both the upstream (magnetosheath) and downstream (magnetosphere) plasma conditions, nearly all empirical models of solar wind - magnetosphere coupling assume this process is one-way. That is to say, coupling functions predict the energy transport or open magnetic flux change at the magnetopause as dependent only on the upstream solar wind conditions. In this work we test the simplifying hypothesis that solar wind - magnetosphere coupling is one-way by using a numerical experiment. The Space Weather Modeling Framework (SWMF) is used in the Geospace configuration to simulate Earth's magnetosphere under steady solar wind input conditions with typical driving solar wind inputs and dipole tilt. A 48 - hour test is simulated with the IMF conditions changing every two hours. This test is repeated with constant plasma conditions 9 times, for a total of 216 steady state solar wind conditions. The MHD output data is used to identify the magnetopause and calculate energy flux through the open magnetopause as a direct measure of solar wind - magnetsophere coupling. It is found that while the empirical coupling functions predict trends in the average energy flux through the magnetopause, there is significant variability as measured by the total variation. The results of this numerical experiment refute the one-way coupling hypothesis and highlight the need for an empirical coupling function which includes magnetosphere effects.