Active Latitude Oscillations Observed on the Sun

TL;DR

This study analyzes sunspot active latitudes over six solar cycles using advanced spectral methods, revealing consistent rotation periodicities and oscillating latitudinal drifts, with specific mid-term periodicities appearing in certain cycles.

Contribution

It provides a detailed analysis of active latitude periodicities and latitudinal drifts across multiple solar cycles using Multi Taper and Wavelet methods, highlighting new cycle-specific periodicities.

Findings

Solar rotation periodicities (26-38 days) are present in all cycles.

Active latitudes drift towards the equator following an oscillating path.

A 300-370 day periodicity appears in certain cycles and hemispheres.

Abstract

We investigate periodicities in mean heliographic latitudes of sunspot groups, called active latitudes, for the last six complete solar cycles (1945-2008). For this purpose, the Multi Taper Method and Morlet Wavelet analysis methods were used. We found the following: 1) Solar rotation periodicities (26-38 days) are present in active latitudes of both hemispheres for all the investigated cycles (18 to 23). 2) Both in the northern and southern hemispheres, active latitudes drifted towards the equator starting from the beginning to the end of each cycle by following an oscillating path. These motions are well described by a second order polynomial. 3) There are no meaningful periods between 55 and about 300 days in either hemisphere for all cycles. 4) A 300 to 370 day periodicity appears in both hemispheres for Cycle 23, in the northern hemisphere for Cycle 20, and in the southern hemisphere for Cycle 18.