The Day the Sun Stood Still: Using global Thermodynamic MHD Simulations to Infer the Structure of the Solar Corona and Inner Heliosphere during the Maunder Minimum

Observations of the Sun's corona during the space era have led to a picture of relatively constant, but modulating solar output and structure. Longer-term, more indirect measurements, such as from Beryllium-10, coupled by other albeit less reliable contemporaneous reports, however, suggest periods of significant departure from this standard, which, in turn, may have produced terrestrial weather effects. The Maunder Minimum, was one such epoch where: (1) Sunspots effectively disappeared for long intervals during a 70-year period; (2) Eclipse `observations' suggested the distinct lack of a visible K-corona but possible appearance of the F-corona; (3) Reports of aurora were notably reduced; and (4) Cosmic ray intensities at Earth were substantially higher. Using a global thermodynamic MHD model, we constructed a broad range of possible coronal configurations for the Maunder Minimum period and compared their predictions with these limited observational constraints. We conclude that the most likely state of the corona during the Maunder Minimum was not merely that of the 2008/2009 solar minimum, as has been suggested in several recent studies. Instead, we argue that the Sun's photospheric magnetic field was substantially reduced (by up to an order of magnitude) and this led to, and is consistent with the observations associated with this period. We discuss the implications of this work in terms of future long-term space weather forecasting.