Our Sun experiences a regular 11-year cycle of activity, which is measured from minimum to minimum. An international panel of experts has now confirmed that we have entered a new cycle, after the previous one reached a minimum in December 2019.
We've now entered Solar Cycle 25, the 25th since reliable records of solar activity begun. The natural cycle is fairly regular, experiencing calm and stormy activity lasting roughly 11 years, but over the last couple of centuries there have been exceptions to this rule. The level of activity also changes, making predictions and confirmation of the cycle's minimum and maximum difficult, which is why it was only announced yesterday, despite the minimum occurring in December.
“The most important thing to remember with predictions is, you’re going to be wrong,” Dean Pesnell, a solar cycle expert at NASA's Goddard Space Flight Center, said in a statement. “You’re never going to be perfect. It’s what you learn from that, that allows you to make progress in your predictions.”
The international Solar Cycle 25 Prediction Panel was co-sponsored by NASA and the National Oceanic and Atmospheric Administration (NOAA). To help work out when a cycle has ended and a new one has begun, researchers use solar spots as a convenient proxy for activity. These are associated with events like solar flares and coronal mass ejections, so the fewer spots observed the calmer the Sun is.
Towards the minimum, our star goes for weeks and even months without any of these dark blotches on its surface. But we can only confirm that the minimum was surpassed when the activity and the number of sunspots start picking up again. So, it's not surprising that it takes many months to say “Yep, that was the minimum!”
The international panel uses observations collected by the World Data Center for the Sunspot Index and Long-term Solar Observations, located at the Royal Observatory of Belgium. With that data, they have predicted that the next solar maximum will happen in July 2025.
“As we emerge from solar minimum and approach Cycle 25’s maximum, it is important to remember solar activity never stops; it changes form as the pendulum swings,” Lika Guhathakurta, a solar scientist at the Heliophysics Division at NASA Headquarters in Washington, explained in a statement.
Cycle 25 is expected to be of a similar activity level as Cycle 24, which was actually weaker than average, but this doesn’t mean we should lower our guards. The Sun's activity shapes the space weather around our planet and the release of powerful solar flares can disrupt communication satellites and cause havoc for technologies on Earth.
“Just because it’s a below-average solar cycle, doesn’t mean there is no risk of extreme space weather,” Doug Biesecker, panel co-chair and a solar physicist at NOAA’s Space Weather Prediction Center (SWPC) said. “The Sun’s impact on our daily lives is real and is there. SWPC is staffed 24/7, 365 days a year because the Sun is always capable of giving us something to forecast.”
The most powerful geomagnetic storm on record is the Carrington Event of 1859. A massive solar flare threw so many high-energy particles towards Earth that both the Northern and Southern lights were visible from the poles to the tropics, waking up birds and those who rise with the Sun around the world. These charged particles were also responsible for starting fires in telegraph stations and shocking operators across the US and Europe. If it were to happen today, estimates put the cost at something in the order of trillions of dollars for the US alone. So, it's best we keep an eye on the Sun and its activity.