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Abstract

Direct information on space climate – the background on which space weather manifests – is limited to the space era, that began only in 1964. Before that date the only information on the solar – terrestrial relationship could be retrieved from the geomagnetic field variations recorded at geomagnetic observatories, thus extending back with ~150 years the information on the space climate, based on geomagnetic indices. Reconstructions of certain parameters of the solar activity to 1700, based on physical models and correlations, which we show here, present, besides the well-known decadal variation, related to solar cycles in the solar activity, variations at time scales of the Hale, magnetic and Gleissberg, ‘long’ solar cycles. We find that variations at inter-decadal (20-30 years) and sub-centennial (60-90 years) time scales are present in both geomagnetic observatories data and in some long-term models of the main geomagnetic field, such as gufm1 (Jackson et al., 2000). Based on such data the evolution of the space climate is discussed for the entire time interval of the validity of the model gufm1 (1590-1960).