Abstract/Summary

Using the reconstruction of power input to the magnetosphere presented in Paper 1 (Lockwood et al., 2017a), we reconstruct annual means of the geomagnetic Ap and AE indices over the past 400 years to within a 1-sigma error of +/- 20%. In addition, we study the behaviour of the lognormal distribution of daily and hourly values about these annual means and show that we can also reconstruct the fraction of geomagnetically-active (storm-like) days and (substorm-like) hours in each year to accuracies of 50-60%. The results are the first physics-based quantification of the space weather conditions in both the Dalton and Maunder minima. Looking to the future, the weakening of Earth’s magnetic moment means that the terrestrial disturbance levels during a future repeats of the solar Dalton and Maunder minima will be weaker and we here quantify this effect for the first time.