WITH A SOLAR CYCLE PREDICTOR
As the Sun reawakens from the low point in its 11-year pattern of activity, a group of scientists has predicted what the new solar cycle will be like
What is the solar cycle?
It’s the cycle of sunspots that is driven by the Sun’s evolving magnetic field. They appear at the beginning of a solar cycle, starting at high latitudes with very few of them. As the solar cycle progresses, they become much more frequent and move to lower latitudes, peaking at a solar maximum; then there’s a declining phase. The solar cycle has a period of about 11 years and we’ve got records of the last 24 cycles.
You’re a member of the
Solar Cycle 25 Prediction
Panel – what is that?
Every solar cycle there is an international organisation that convenes a group of experts to make predictions about the next solar cycle. Back in 2019 we asked solar scientists to submit their predictions to us and then we used them to come up with a consensus as to how we thought the next solar cycle would be. The predictions are also for those outside the solar community; as the more sunspots there are, the more solar flares, coronal mass ejections and coronal holes there are and these kinds of activity can impact us here on Earth. We’re mostly protected by Earth’s magnetic field, but astronauts or satellites in space can be very much impacted by these solar storms.
What were your predictions?
We’re officially charged with predicting the solar minimum, the maximum and the amplitude, but we also like to estimate some other things like how many flares there might be. We predicted that solar minimum would occur in April 2020, plus or minus six months. It took a while to say for sure when the solar minimum was – as we take a 13-month average of sunspot numbers – so we don’t know we’ve passed the minimum until at least six months afterwards. In the last month or two we’ve been able to look back and see that minimum occurred in December 2019.
We also predicted the solar maximum to be in July 2025, plus or minus six months, but because the minimum shifted earlier it might be closer to the ▲ 2006 2005 beginning of 2025. That said, the timing of the maximum is a little bit less clear. In Solar Cycle 24, for example, there were two pronounced peaks two years apart. Is the maximum timed with the first peak, the second peak or somewhere in the middle? So it’s a rough estimate.
How did you make those predictions?
There are three different ways. First, there are numerical methods, where you look at the historical records of solar cycles and see if you can use statistical analysis to guess what the next cycle will be. The second set of approaches are more physics-based; these look at the science of what’s going on in the Sun and then use that knowledge to try and make predictions. This includes looking at the geomagnetic activity here on Earth or the strength of the Sun’s polar magnetic field. The final option encompasses anything that wouldn’t fit into the other categories. You get all kinds of things – like people looking at the orbit of Jupiter; there’s been very little evidence to substantiate that, but there are all kinds of ideas. Overwhelmingly though, we find the physics-based methods have been more effective.
How is Solar Cycle 25 looking?
It’s looking like it’s going to be right on par with Solar Cycle 24, which was the weakest cycle we’ve had in the last 100 years. But little cycles happen and it’s not so small that we’re worried the Sun is dying or anything. One of the things that will be interesting to see is if, after 25 the cycles, it starts to ramp up again.
Can you make any predictions for future cycles?
We really are very limited and can only predict the next cycle when we’re close to the end of the previous one. We’re not going to be able to say anything about Solar Cycle 26 for another eight or nine years. That’s a big motivator for the kind of science and research that we’re doing, but whether there’s a fundamental limit to how far you can predict future solar activity remains an open question.