The Sun Is Being Weird. It Could Be Because We’re Looking at It All Wrong

Solar flare erupting from a sunspot [image credit: space.com]

Who knew!? – asks ScienceAlert. The article links to an interesting new paper on solar cycles, which makes some predictions for the current SC 25 (see section 3.2: Forecasting Using the Solar Unit Cycle). One of those is that it should end in October 2031 ± 9 months, and the authors go on to suggest forthcoming NASA and ESA missions make it probable that ‘Cycle 25 will be the last solar activity cycle that is not fully understood.’
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Something weird is going on with the Sun.

So far, almost every day in 2022 it has erupted in flares and coronal mass ejections, some of which were the most powerful eruptions our star is capable of.

By itself, an erupting Sun is not weird. It erupts regularly as it goes through periods of high and low activity, in cycles that last roughly 11 years.

The current activity is significantly higher than the official NASA and NOAA predictions for the current solar cycle, and solar activity has consistently exceeded predictions as far back as September 2020.

But a solar scientist will tell you that even this isn’t all that weird.

“We can’t reliably predict solar cycles,” solar astrophysicist Michael Wheatland of the University of Sydney, Australia told ScienceAlert.

“We don’t completely understand the solar dynamo, which generates the magnetic fields seen at the surface as sunspots, and which produce flares. This is one of the outstanding problems in astrophysics; the inaccuracy in the prediction is unsurprising.”

Unsurprising, sure. But what if that very lack of surprise – that we expect to be bad at predicting solar cycles – means we need to completely rethink how we do it? What if we’re basing our predictions on the wrong metric?

From 11 to 22 years

Solar cycles have a huge impact on the Solar System but are relatively poorly understood. Scientists have ascertained that they seem inextricably linked with the solar magnetic field, which arcs across the surface of our Sun in twists, swirls, and loops.

Roughly every 11 years, the Sun’s magnetic poles flip, north becoming south and vice versa. This switch coincides with what is known as solar maximum, characterized by a peak of sunspot, flare, and coronal mass ejection (CME) activity.

Following this reversal, activity lessens, before ramping up towards a peak once more. This is where we are now – the escalation phase of the current cycle, the 25th since we started counting.

Activity cycles are characterized and predicted based on one metric: the number of sunspots seen on the Sun. These are temporary regions where magnetic fields are particularly strong, facilitating the eruption of flares and CMEs. They appear as dark spots because the magnetic field inhibits the flow of hot plasma, and the regions are subsequently cooler and dimmer than their surroundings.

According to solar physicist Scott McIntosh of the US National Center for Atmospheric Research, predicting solar cycles based on how many sunspots we count is a problem.

“The sunspot cycle is not the primary thing. It’s a secondary thing,” he told ScienceAlert. “And the way the canon is written, the way the textbooks are written, the way solar activity is presented, it’s portrayed as the primary.

“The problem is that it’s really not, and the underlying Hale cycle, the 22-year magnetic cycle, is the primary. And the sunspot cycle is just a tiny subset of this bigger picture.”

Continued here.