Deciphering Solar Magnetic Activity: 140 Years Of The `Extended Solar Cycle' -- Mapping the Hale Cycle

TL;DR

This study analyzes 140 years of solar observational data to reveal that the extended solar cycle (ESC) and Hale cycle are recurrent phenomena, with the ESC playing a fundamental role in solar magnetic activity and sunspot production.

Contribution

It demonstrates that the ESC is a fundamental component of the solar magnetic cycle, linked to the Hale cycle, and clarifies its relation to sunspot activity using a consistent analysis method.

Findings

ESC is recurrent over 140 years of data.

Maunder's butterfly pattern is a subset of the Hale cycle.

55-degree latitude is crucial in solar magnetism evolution.

Abstract

We investigate the occurrence of the "extended solar cycle" (ESC) as it occurs in a host observational data spanning 140 years. Investigating coronal, chromospheric, photospheric and interior diagnostics we develop a consistent picture of solar activity migration linked to the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA) using previously identified Hale cycle termination events as the key time for the SEA. Our analysis shows that the ESC and Hale cycle, as highlighted by the terminator-keyed SEA, is strongly recurrent throughout the entire observational record studied, some 140 years. Applying the same SEA method to the sunspot record confirms that Maunder's butterfly pattern is a subset of the underlying Hale cycle, strongly suggesting that the production of sunspots is not the fundamental feature of the Hale cycle, but the ESC is. The ESC (and Hale cycle) pattern highlights the importance of 55\degree\ latitude in the evolution, and possible production, of solar magnetism.