Deciphering solar magnetic activity: on grand minima in solar activity

Scott W Mcintosh,Robert J Leamon

doi:10.3389/fspas.2015.00002

Abstract

The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magnetism, perhaps even indicators of a significant downward trend, over recent decades. Are we entering a minimum in solar activity that is deeper and longer than a typical solar minimum, a minimum? How could we tell if we are? What is a grand minimum and how does the Sun recover? These are very pertinent questions for modern civilization. In this paper we present a hypothetical demonstration of entry and exit from grand minimum conditions based on a recent analysis of solar features over the past 20 years and their possible connection to the origins of the 11(-ish) year solar activity cycle.

Highlights

We live in the outer atmosphere of our star
We compare the observed variation of signposts over the past 70 years with the hypothetical model to illustrate where we may be in the progression to grand minimum should the apparent downturn in solar magnetism continue
Using observations from soho/EIT, soho/MDI, sdo/AIA, and sdo/HMI that span from 1996 to 2014, they deduced that the landmarks and phases of the 11-ish year sunspot cycle: the ascending phase, solar maximum, the declining phase, and solar minimum arise as a result of the latitudinal-temporal interaction of magnetic flux systems that belong to the 22-year magnetic activity cycle

Summary

Introduction

We live in the outer atmosphere of our star. As a result, the electromagnetic radiation from our star is an essential ingredient in our day-to-day existence and, as our civilization becomes increasing dependent on technology, we become increasingly susceptible to our star’s occasional tantrums. We discuss the concept of magnetic activity band interaction in the context of solar cycle 23 as originally discussed by McIntosh et al (2014a) and use the phenomenological description of solar cycle modulation described therein to present a hypothetical progression of our Sun into (and out of) grand (sunspot) minima.

Results

Conclusion