Statistical properties of flares and sunspots over the solar cycle

TL;DR

This paper reviews statistical analyses of solar activity indices, highlighting patterns and shifts over solar cycles, especially cycle 23, and discusses implications for understanding solar dynamics and long-term activity trends.

Contribution

It provides a comprehensive review of statistical properties of solar activity indices, revealing a 22-year pattern and analyzing the peculiarities of cycle 23 within long-term solar activity.

Findings

Shifts of 1-2 years between activity peaks of different indices.

A 22-year pattern in activity shifts linked to solar dynamo processes.

Cycle 23's minimum not exceptional, indicating typical variability.

Abstract

The present paper reviews results derived from statistical studies on solar activity indices. The prolonged minimum phase of cycle 23 raised the question of peculiarities inherent in cycle 23. The most important solar activity index is the relative sunspot number and though most of other indices are closely related, shifts are obtained between their peak activity of the order of 1-2 years. These shifts reveal a 22-yr pattern which can be attributed to solar interior or dynamo related processes. The minimum phase of cycle 23 is not found to be exceptional. Investigating the relative sunspot numbers over the past 150 years, solar cycles of more prolonged minima are observed. Since 1920 solar activity is quite high ('modern maximum') and cycle 23 might be the herald of the end of this phase.