Speaker
Description
Solar cyclic activity was discovered in the 19$^\textrm{th}$ century and traced back to 1610 CE through directly observed sunspots. Using indirect cosmogenic proxy data, such as $^{14}$C in tree trunks and $^{10}$Be in ice cores, it is possible to reconstruct long-term solar activity back for several millennia, but individual cycles were not readily resolved. Thanks to the recent breakthrough in the precision of $^{14}$C measurements, cyclic solar activity can now be reconstructed over millennia using precise annually resolved radiocarbon data.
Here, we present a detailed reconstruction of solar cyclic activity, via annual sunspot numbers (SNs), during the first millennium CE. This period includes one extreme solar event occurring in 774 CE and one Grand solar minimum covering 650—730 CE. A total of 91 solar cycles were identified for the first millennium CE, including 26, 24, and 41 cycles, which were well, reasonably, and poorly defined, respectively.
We perform a statistical analysis of the reconstructed cycles, focusing on the distributions of cycle lengths, amplitudes, and shapes (Waldmeier’s relations). We also discuss the reliability of the solar cycle definition during grand solar minima. The statistical results are compared with those for other periods of known solar cyclic activity