Solar modulation during the Holocene

Abstract

We built a composite of three reconstructions of the solar modulation function over the Holocene. The reconstructions until 1950 are based on data from cosmogenic radionuclides and the present time (1951-2004) on neutron monitor data. Interpreting our composite as an index of solar activity, we were able to compare the current solar activity with the last 9 300 years. During this time span 25 periods with similar high activity than the current period were found. That corresponds to about 15% of the time which lead to the conclusion that currently the Sun is very but not exceptionally active. Our composite has a large potential for studies dealing with solar activity like the understanding of the solar dynamo and the reconstruction of solar forcing.