Sun hitting peak sunspot activity

Over recent weeks and months, the Sun has been extremely active. It has not only excited physicists and cosmologists, but it’s also meant that the northern and southern lights have been visible at far lower latitudes than normal with people posting dramatic images from their neighbourhoods on social media. But just how unusual is this intense period of solar activity? Ryan French is a physicist at the National Solar Observatory, and author of 'The Sun: Beginner's guide to our local star’...

Ryan - So the Sun at the moment is entering this period we call solar maximum. The Sun follows an 11 year cycle of increasing and decreasing activity on the Sun. At the bottom of this cycle, there are no solar flares, no sunspots, no eruptions on the Sun. But at the moment, at this point, sort of last year into this year, through to next year, we're in this phase of solar maximum where there are lots of flares, lots of eruptions, and so you're likely seeing a lot of new stories because of that.

Chris - So we define the Sun's cycle in its activity by the presence of these flares and sunspots and so on. They're the kind of visible manifestation that the Sun is behaving differently?

Ryan - That's correct, yes. So sunspot specifically, there are these dark structures on the Sun. This is where flares and eruptions originate from these sunspot regions. So the solar cycle is literally just defined by counting the number of sunspots on the Sun every day. And that count follows this nice 11 year cycle.

Chris - And how far back do records go?

Ryan - They go back all the way to the 1700s. Back then they weren't counting sunspots as we are now. The official count didn't start until the mid 1800s, but right now we are in solar cycle 25. So if you multiply 25 by 11, that takes you back way into the 1800s.

Chris - And are there any other changes apart from these sunspots and the flares and so on, which perhaps we'll come to in a second. Are there any other changes in how the Sun behaves when it goes through this 11 year cycle?

Ryan - So there's a few different changes, but they're all kind of interconnected. So the total brightness of the Sun varies very slightly throughout this period. The magnetic field of the Sun actually flips throughout this 11 year solar cycle and the complexity of the magnetic field in the Sun's atmosphere, which does cause all these flares and exciting events, varies a lot too.

Chris - And how do those flares when one happens? How do they affect us?

Ryan - Yeah, so solar flares can affect us in a couple of key different ways. The first of all is from the flare itself. So a solar flare is just a conversion of energy from the magnetic field of the Sun into primarily light, mostly X-rays. And when those x-rays are produced from these solar flares, they can hit the upper atmosphere of the Earth. That can expand the upper atmosphere slightly. This can cause a sort of what we call radio blackout. So radio waves cannot propagate quite as well. Communication to satellites doesn't work quite as effectively. But the second probably more crucial element of these flares is not the flare itself, but about half of solar flares, a coronal mass ejection, which just a bunch of stuff from the Sun launches out into space. And if that arrives at Earth, it not only produces beautiful Northern Lights displays like we saw earlier this year back in May, but that also has the ability to impact the power grid and satellites as well.

Chris - So it's pretty important that we monitor it because of the impact on us that that could have. Is that becoming more common or are these events when they occur intensifying?

Ryan - Yeah, that's a great question. Certainly it is very important for us to understand these events, and there's a massive global effort worldwide to try and improve our understanding both at the Sun and when it arrives at Earth. At the end of the day, there's nothing unusual going on at the moment. We're entering this phase of solar maximum, as I said before. So these events are more common. As events are more common, there are higher chances of very, very big events. The one in May, for example, was the biggest event that we'd had for 20 years or so. And that's a pattern across all of these phenomena. Actually, this solar cycle that is peaking at the moment is already bigger than the previous solar cycle that peaked back in 2014 or so and more in line with solar cycles that peaked back in 2003 and beforehand as well.

Chris - So do you think then that although we've got this 11 year cycle superimposed on that, or at least that could be superimposed on a bigger cycle, which is that gradually these things increase over time, perhaps cyclically and that we're going to see even more intense activity in the years ahead?

Ryan - It's quite possible. We do think that these solar cycles might be imposed by a greater cycle, as you said. But, we're just coming out of the very minimum of that sort of second grander cycle, we believe. So the highest solar activities we've ever measured were actually back in the 1970s and 80s, and we're still way away from the levels observed during that period, even though we are now more active than we were a decade ago.