The 8-Year Solar Cycle During the Maunder Minimum

The presence of grand minima, characterized by significantly reduced solar and stellar activity, brings a challenge to the understanding of solar and stellar dynamo. The Maunder Minimum (1645-1715 AD) is a representative grand solar minimum. The cyclic variation of solar activity, especially the cycle length during this period, is critical to understand the solar dynamo but remains unknown. By analyzing the variations in solar activity-related equatorial auroras recorded in Korean historical books in the vicinity of a low-intensity paleo-West Pacific geomagnetic anomaly, we find clear evidence of an 8-year solar cycle rather than the normal 11-year cycle during the Maunder Minimum. This result provides a key constraint on solar dynamo models and the generation mechanism of grand solar minima. The solar cycle length during the Maunder Minimum is vital for understanding the appearance of the grand solar minimum. However, owing to the limited data quality of the currently used solar activity proxies, the cyclic variation of solar activity still needs to be explored during the Maunder minimum. Here, we show definitive observational evidence of an 8-year solar cycle during the Maunder Minimum using historical observations of equatorial aurorae. The 8-year solar cycle length found here provides a pivotal clue to understanding the origin and predictability of the grand solar minimum. Give a definitive observational evidence of an 8-year solar cycle during Maunder MinimumThe distinct solar dynamo during the Maunder Minimum is not chaoticA consistent dynamo explanation is a superposition of the dipole (22 years) and the quadrupole (similar to 13-15 years) with nearly equal amplitude

Automated summary

This study provides definitive observational evidence that an 8-year solar cycle existed during the Maunder Minimum, which has important implications for solar dynamo models and the generation mechanism of grand solar minima.