About 200-Year Cycle of Solar Activity in the Mediaeval Korean Records and Reconstructions from Cosmogenic Radionuclides

TL;DR

This study uncovers a 200-year solar activity cycle in Korean and Chinese historical records, challenging the notion that solar cycles are only 11 years, and introduces a new method to analyze cycle stability.

Contribution

The paper demonstrates a 200-year cycle in solar activity using historical records and a novel samplogram method to assess cycle stability, revealing complex cycle behaviors.

Findings

Identification of a 200-year solar cycle in historical records

Introduction of the samplogram method for cycle stability analysis

Evidence that grand minima are not obligatory within the 200-year cycle

Abstract

We investigated the Korean records of naked-eye sunspot observations and found an implication of periodicity of about 200-year. Adding the Chinese records we showed that the historical naked-eye sunspot observations have the similar periodicity. Recent some works showed that there would be no intrinsic periodicities except 11-year cycle. We adopt the new approach called samplogram to test sampling stability of cycles in terms of power spectra and difference series and show that the Suess/de Vries cycle of about 207-year is a deterministic cycle of the stochastic solar activity. Also we show that occurrences of grand minimum are not necessarily expected with the Suess/de Vries cycle and it is possible to appear double or multiple grand maxima without a grand minimum within them.