Speaker
Description
Direct sunspot observations cover about four centuries or about 36 solar cycles, with one-third of them being poorly defined because of the lower quality of observations before 1750. An indirect proxy of solar activity, the abundance of cosmogenic isotopes measured in independently dateable natural archives, such as 14C in tree rings, is the only quantitative method to reconstruct solar activity before that. However, because of the insufficient accuracy of the isotope measurements, individual solar cycles could not be resolved earlier. Significant progress has been achieved recently with the precision AMS measurements of 14C (Brehm et al., 2021, 2025), which have made it possible to reconstruct solar cycles over the past millennia. Using the new annual-resolution 14C data and full-chain modelling, solar cycles have been reconstructed for the last millennium (83 cycles, Usoskin et al., 2021) and the first millennium BC (93 cycles, Usoskin et al., 2025). This makes the total number of reconstructed solar cycles about 200. Although not all reconstructed cycles are well defined, some statistical features can be studied. Herewith, we present the results of the solar cycles' statistical analyses, including the cycle lengths, features of grand minima, multimodality of the cycle strength distribution, and a check of empirical rules, e.g., the simplified Waldmeier rule.
| Do you plan to attend in-person or online? | In-person |
|---|
