Transitional dynamics of the solar convection zone

TL;DR

This paper analyzes the transition in solar activity dynamics over time, showing a shift from turbulent convection dominance in the historic period to more active inner layer dynamics in recent decades, supported by cluster analysis and geomagnetic data.

Contribution

It introduces a novel cluster analysis approach to study solar activity fluctuations, revealing a transition in the underlying convection zone dynamics between historic and modern periods.

Findings

Historic period shows strong clustering in sunspot activity.

Modern period exhibits random, white noise-like fluctuations.

Cluster properties support a shift from turbulent to active inner layer dynamics.

Abstract

Solar activity is studied using a cluster analysis of the time-fluctuations of sunspot number. In the historic period (1850-1932) the cluster exponent was approximately equal to 0.37 (strong clustering) for the high activity components of the solar cycles. In the modern period (last seven solar cycles: 1933-2007) the cluster exponent was approximately equal to 0.50 (random, white noise-like). Comparing these results with the corresponding data from laboratory experiments on convection it is shown, that in the historic period emergence of sunspots in the solar photosphere was dominated by turbulent photospheric convection. In the modern period, this domination was broken by a new more active dynamics of the inner layers of the convection zone. Cluster properties of the solar wind magnetic field and the aa-geomagnetic-index also support this result. Long-range chaotic dynamics in the solar activity is briefly discussed.