Fluctuations in the Alpha-Effect and Grand Solar Minima

TL;DR

This paper estimates the Babcock-Leighton fect parameters from sunspot data, finds significant fluctuations, and models their impact on solar magnetic cycles, reproducing grand minima and maxima consistent with Holocene observations.

Contribution

It introduces a method to estimate fect fluctuations from sunspot data and incorporates them into a dynamo model to explain long-term solar activity variations.

Findings

Fluctuation amplitude exceeds the mean fect value.

Model reproduces irregular magnetic cycle changes over centuries.

Statistical characteristics match Holocene solar activity data.

Abstract

Parameters of a special kind of \alpha-effect known in dynamo theory as the Babcock-Leighton mechanism are estimated using the data of sunspot catalogs. The estimates evidence the presence of the Babcock-Leighton \alpha-effect on the Sun. Fluctuations of the \alpha-effect are also estimated. The fluctuation amplitude appreciably exceeds the mean value, and the characteristic time for the fluctuations is comparable to the period of the solar rotation. Fluctuations with the parameters found are included in a numerical model for the solar dynamo. Computations show irregular changes in the amplitudes of the magnetic cycles on time scales of centuries and millennia. The calculated statistical characteristics of the grand solar minima and maxima agree with the data on solar activity over the Holocene.