155-day Periodicity in Solar Cycles 3 and 4

TL;DR

This study investigates the presence of a 155-day solar periodicity, known as Rieger periodicity, during solar cycles 3 and 4 by analyzing aurora observations from the late 18th century using spectral analysis methods.

Contribution

It introduces a novel analysis of historical aurora data to detect Rieger periodicity during early solar cycles, overcoming limitations of sunspot data quality.

Findings

Probable presence of Rieger periodicity in cycles 3 and 4

Spectral analysis confirmed the periodicity in cycle 3

Histograms suggest periodicity during both cycles

Abstract

The near 155 days solar periodicity, so called Rieger periodicity, was first detected in solar flares data and later confirmed with other important solar indices. Unfortunately, a comprehensive analysis on the occurrence of this periodicity during previous centuries can be further complicated due to the poor quality of the sunspot number time-series. We try to detect the Rieger periodicity during the solar cycles 3 and 4 using information on aurorae observed at mid and low latitudes. We use two recently discovered aurora datasets, observed in the last quarter of the 18th century from UK and Spain. Besides simple histograms of time between consecutive events we analyse monthly series of number of aurorae observed using different spectral analysis (MTM and Wavelets). The histograms show the probable presence of Rieger periodicity during cycles 3 and 4. However different spectral analysis applied has only confirmed undoubtedly this hypothesis for solar cycle 3.