The modern high solar activity: How unusual is it?
Abstract
The history of direct solar observations is 400-years long, but for many purposes longer series are needed. On the longer time scales, indirect proxy data like cosmogenic nuclides should be used to evaluate the past level of solar activity. Here I present a reconstruction of the solar activity on the multi-millennial time scale using physics-based models for the whole chain of processes between the Sun and Earth. The reconstructed activity depicts great variability, from grand minima with almost vanishing sunspot activity to grand maxima, when the activity was comparable to the contemporary high activity level. The fraction of time that the Sun spends in grand minima and hyper-active states is evaluated. In particular, these reconstructions imply that the contemporary high level of solar activity is quite exceptional on the multi-millennial time scale. Possible uncertainties of reconstructions are discussed in details, including random errors as well as systematic uncertainties, related, e.g., to the geomagnetic field model. The conclusion about the unusually high contemporary level of solar activity on the multi-millennial time scale is confirmed to be robust by using different methods. Implications for the solar dynamo and solar-terrestrial connections are discussed as well.
- Publication:
-
IAU Joint Discussion
- Pub Date:
- August 2006
- Bibcode:
- 2006IAUJD...8E..14U