"Solar cycle 25: why aurora sightings spread so far south"
In May 2024 people photographed the northern lights from places that almost never see them - across much of the United States and southern Europe. It wasn't a fluke of social media; it was the Sun's activity cycle near its peak.
The 11-year cycle
The Sun's activity rises and falls over roughly 11 years. At solar maximum there are more sunspots, more flares and more coronal mass ejections (CMEs) - huge clouds of magnetised plasma that, when aimed at Earth, cause geomagnetic storms. At solar minimum the Sun can go weeks with almost no spots.
The current cycle, Solar Cycle 25, began in late 2019. In October 2024, NASA and NOAA announced that the Sun had reached its solar maximum period.
The May 2024 storm
On 10-11 May 2024 a series of CMEs reached Earth and produced the first G5 (extreme) geomagnetic storm in over twenty years. Aurora was reported far further south than usual on both sides of the Atlantic, and in the southern hemisphere too. Another strong storm in October 2024 brought widespread sightings again.
What happens after the peak
Activity doesn't switch off after solar maximum. The declining phase of a cycle often still brings strong storms, and fast solar-wind streams from coronal holes become more common, producing repeated moderate storms on a roughly 27-day rhythm as the Sun rotates. The overall trend is fewer extreme events each year as the cycle heads towards its next minimum, expected around the end of the decade.
For aurora watchers, that means:
- Big, far-south storms become rarer, but aren't over.
- Moderate storms (Kp 5-6) keep happening and are worth watching for at higher latitudes.
- The equinox months (March-April and September-October) tend to bring more geomagnetic activity than the solstices, a well-documented seasonal pattern.
How to not miss the next one
- Watch NOAA's 3-day Kp outlook for G1+ watches, then the live Kp on the night.
- A CME usually takes 1-4 days to reach Earth, so news of a big flare gives you a little notice.
- Keep a dark-sky spot in mind in advance, with a clear view north.
- Remember clouds: a G4 storm behind thick cloud shows you nothing.
Nobody can promise a date. But the years around and after solar maximum are among the best chances many people will have this decade.