Hemispheric Asymmetries of Solar Photospheric Magnetism: Radiative, Particulate, and Heliospheric Impacts

TL;DR

This paper investigates hemispheric asymmetries in solar magnetic activity and their impacts on the heliosphere, revealing persistent asymmetries, their historical evolution, and potential implications for future solar minima.

Contribution

It provides new insights into the hemispheric phase differences, their historical changes, and their influence on solar radiative, particulate, and cosmic ray fluxes.

Findings

Hemispheric asymmetry in solar magnetism is persistent and evolving.

Historical analysis shows hemispheric dominance has shifted twice in 130 years.

Current asymmetry may lead to future low in solar radiative and particulate output.

Abstract

Among many other measurable quantities the summer of 2009 saw a considerable low in the radiative output of the Sun that was temporally coincident with the largest cosmic ray flux ever measured at 1AU. A hemispheric asymmetry in magnetic activity is clearly observed and its evolution monitored and the resulting (prolonged) magnetic imbalance must have had a considerable impact on the structure and energetics of the heliosphere. While we cannot uniquely tie the variance and scale of the surface magnetism to the dwindling radiative and particulate output of the star, or the increased cosmic ray flux through the 2009 minimum, the timing of the decline and rapid recovery in early 2010 would appear to inextricably link them. These observations support a picture where the Sun's hemispheres are significantly out of phase with each other. Studying historical sunspot records with this picture in mind shows that the northern hemisphere has been leading since the middle of the last century and that the hemispheric "dominance" has changed twice in the past 130 years. The observations presented give clear cause for concern, especially with respect to our present understanding of the processes that produce the surface magnetism in the (hidden) solar interior - hemispheric asymmetry is the normal state - the strong symmetry shown in 1996 was abnormal. Further, these observations show that the mechanism(s) which create and transport the magnetic flux magnetic flux are slowly changing with time and, it appears, with only loose coupling across the equator such that those asymmetries can persist for a considerable time. As the current asymmetry persists and the basal energetics of the system continue to dwindle we anticipate new radiative and particulate lows coupled with increased cosmic ray fluxes heading into the next solar minimum.