The New Sunspot Number Series in Comparison to Cosmogenic Radionuclide Based Solar Activity Reconstructions

Abstract:

The solar modulation of galactic cosmic rays leads to variations in the production rates of cosmogenic radionuclides such as 10Be and 14C. These particles can be measured in tree rings (14C) and ice cores (10Be), and cosmogenic radionuclide records can be used for solar activity reconstructions far back into the past. However, cosmogenic radionuclides are not only influenced by solar variability but also by climate effects on the deposition processes into natural archives. Such climate effects have led to disagreeing 10Be records for the past centuries and to disagreeing reconstructions of solar activity based on cosmogenic radionuclides. Records from Greenland ice cores appear to indicate a strong increase in solar activity during the recent centuries while Antarctic records indicate high but not exceptional solar activity during the second part of the 20th century. Here, we will review the available 10Be records with respect to their agreement and disagreement with the new sunspot number series. In addition, we will show that the new sunspot number series agrees very well with previously published 14C-based reconstructions of past solar activity.