These past couple of weeks, Sun watchers have been enjoying the first sunspots of solar cycle 25. Historically, solar cycles have been measured from minimum to minimum. On average, the separation between minimum is about eleven years, and many of us learned this is due to the periodic inversion of the Sun’s magnetic field as the poles flip. The thing is, solar cycles can be highly variable in both duration and energy, with some cycles lasting more than fifteen years and the sunspot number varying from tens, to more than 200 between years. The most active periods, historically, were notable for the amazing aurora that their flares and coronal mass ejections (CMEs) generated. 

Today, however, we recognize that extreme solar flares and CMEs have the potential to wipe out the power grid and satellites we rely on for weather, communications, and more. Trying to predict the severity of solar flares and of solar maxima, in general, has become the job of space weather forecasters, and like trying to predict hurricane seasons, the consensus of “this will be a bad one” or “this season won’t be too bad” isn’t a very accurate science.

But what if predicting solar cycles could be precise? Well, one team, with a controversial new way of looking at the Sun, thinks maybe it could be, and maybe this upcoming solar cycle will be far harsher than the consensus forecast predicts. 

Researchers at the National Center for Atmospheric Research have published an article in Solar Physics describing how solar cycles should be measured based on when magnetic bands cross one another on the solar equator. This work is led by Scott McIntosh and builds on earlier work that looked at the full 22-year solar cycle and used coronal bright points – ephemeral flickers of extreme ultraviolet light in the solar atmosphere – to study the motions of magnetic bands. The bright points migrate from nearer the poles to the equator over about twenty years. According to the prior research, the crossing of the bright points – and the magnetic bands they are tied to – coincides with the emergence of sunspot activity and marks the beginning of a new solar cycle.

This indicator lags behind the solar minimum in time and occurs after sunspots have begun to appear. It can be more precisely measured than our current use of solar minima, and it can be measured as it occurs.

According to McIntosh: When we look back over the 270-year long observational record of terminator events, we see that the longer the time between terminators, the weaker the next cycle. 

Study co-author Bob Leamon, adds: And, conversely, the shorter the time between terminators, the stronger the next solar cycle is.

This relationship could prove a bit problematic for our power grid and network of satellites because we just completed a very short solar cycle, and that would mean we’re in for an extreme one in the next few years.

Consensus, however, says that the last cycle was really weak, and the next one will be weak. But consensus could mean a lot of people are wrong, and we’re not going to know until this next cycle gets going. Hold onto your hats people, this could be a spotty ride.

Whatever happens, we are ready to watch it in extreme detail. The Daniel K. Inouye Solar Telescope has released its first-ever image of a sunspot. Taken in January 2020, this sunspot is seen with 2.5 times higher resolution than has been previously achieved, and it allows structures as small as 20 kilometers to be seen. This spot is about 10,000 miles or 16,000 km across. This telescope is located on Maui and is still coming online. It is expected to be fully functional in 2021 and will be here to track all the flickers and flares of whatever happens in the next eleven or so years.

More Information

NCAR press release 

NSO press release 

“Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude,” Scott W. McIntosh et al., 2020 Nov 24, Solar Physics.

“The Daniel K. Inouye Solar Telescope – Observatory Overview,” Thomas R. Rimmele, Mark Warner, Charles White, 2020 Dec 4, Solar Physics.