Deciphering Solar Magnetic Activity: 140 Years Of The ‘Extended Solar Cycle’ – Mapping the Hale Cycle

Abstract

The cyclic, enigmatic, and ubiquitous magnetism of the Sun provides the energy we need to survive and has the ability to destroy our technologically dependent civilization. Never before has understanding solar magnetism and forecasting its behavior been so relevant. Indeed, on a broader canvas, understanding solar magnetism is a gateway to understanding the evolution and activity of other stars - the Sun is an astrophysical "Rosetta Stone." Despite the centuries of observation, the past century of precise characterization, and significant advances in theoretical and numerical modeling over the past several decades, we have broken the cypher of the Sun's global-scale magnetism. Using a host of observables spanning 140 years we will revisit an observational concept, the "extended solar cycle," (ESC) that came to the fore in the mid-1980s but almost completely disappeared from the common consciousness of the global solar physics less than a sunspot cycle later - it is unclear why. Using a recently identified solar fiducial time, the end (or "termination") of a solar cycle, we employ superposed epoch analysis to identify the ESC as a mapping of the Sun's fundamental magnetic activity cycle and also as a recurring spatio-temporal unit of solar evolution. The ESC is a pattern from which the spatio-temporal pattern, and numerical modulation, of sunspots is produced. This effort illustrates that the ESC is the manifestation of the Sun's Hale Cycle. We will close by pointing out areas of investigation indicated by the pattern of the Hale Cycle that may permit the conversion from observational correspondence to fundamental physical processes and a leap forward in understanding solar activity.