The Solar Wind - Magnetosphere Coupling Function and Nowcasting of Geomagnetic Activity

We present an semi-empirical derivation of a solar wind - magnetospheric coupling function depending on solar wind parameters and the geometry of their interaction with the Earth including Momentum Flux, Magnetic Reconnection, and Geometric Modulation. The coupling function performs well at all levels of geomagnetic activity at time-scales from one hour and up. We also show how to invert the coupling function, allowing us to infer solar wind parameters in the past ~180 years from the historical geomagnetic record.