Nonaxisymmetric Component of Solar Activity and the Gnevyshev-Ohl Rule

TL;DR

This study uses sunspot vector data to analyze nonaxisymmetric features of solar activity, revealing a 44-year pattern linked to the Gnevyshev-Ohl rule and its anti-rule, indicating complex hemispheric and longitudinal asymmetries.

Contribution

It introduces a vector-based method to quantify solar activity asymmetry, uncovering a 44-year cycle pattern related to the Gnevyshev-Ohl rule in sunspot data.

Findings

The asymmetry modulus varies with the 11-year solar cycle.

The Gnevyshev-Ohl rule and its anti-rule are observed in sunspot asymmetries.

A 44-year structure influences solar activity asymmetries.

Abstract

The vector representation of sunspots is used to study the nonaxisymmetric features of the solar activity distribution (sunspot data from Greenwich - USAF/NOAA, 1874 - 2016).The vector of the longitudinal asymmetry is defined for each Carrington rotation; its modulus characterizes the magnitude of the asymmetry, while its phase points to the active longitude. These characteristics are to a large extent free from the influence of a stochastic component and emphasize the deviations from the axisymmetry. For the sunspot area, the modulus of the vector of the longitudinal asymmetry changes with the 11-year period; however, in contrast to the solar activity, the amplitudes of the asymmetry cycles obey a special scheme. Each pair of cycles from 12 to 23 follows in turn the Gnevyshev - Ohl rule (an even solar cycle is lower than the following odd cycle) or the anti-Gnevyshev - Ohl rule (an odd solar cycle is lower than the preceding even cycle). This effect is observed in the longitudinal asymmetry of the whole disk and the southern hemisphere. Possibly, this effect is a manifestation of the 44-year structure in the activity of the Sun. Northern hemisphere follows the Gnevyshev - Ohl rule in Solar Cycles 12 - 17, while in Cycles 18 - 23 the anti-rule is observed.