From day to day and year to year, our Sun changes in ways that are often missed to occupants of the Earth. People living in the far north like Alaska or the extreme south like Patagonia may see regular solar aurorae, but unless you are paying a lot of attention, you may not notice that these natural light shows have an eleven-year cycle. 

Our Sun’s magnetic field isn’t as stable as Earth’s, and over the course of eleven years, it will go from having a magnetic field that aligns with Earth’s to one that is not or the reverse. When the Sun’s magnetic field is most confused, mid-cycle, we see more solar activity like flares and coronal mass ejections. In a new paper in Solar Physics, researchers led by Mathew Owens looked at how the orientation affected the severity of this activity. And by severity, I mean they looked to see how likely the Sun was to do something dangerous to spacecraft and people outside the Earth’s magnetic field.

In odd-numbered cycles, the Sun’s field starts out in alignment, and in even cycles, it starts flipped relative to our magnetic field. This team found that when the Sun’s field is misaligned with Earth, solar activity has a more severe impact on Earth. Right now, we’re in an odd-numbered cycle, 25, which started in 2019, and we will hit solar maximum, when the Sun is most chaotic, around 2025. And as the sun’s magnetic field settles out to be oppositely aligned, we’re going to go through a period in the late 2020s when the Sun’s activity will be more dangerous. 

While this science is cool on its own, it has one unfortunate real-world side-effect: as our ability to land people on the Moon ramps up at the end of the 2020s, the Sun’s potential to kill people will also be ramping up. During the Apollo program, a major solar eruption in 1972 randomly occurred between Apollo 16 and 17. That was luck. Now, we need to plan how to handle not being so lucky next time.

More Information

University of Reading press release

“Extreme Space-Weather Events and the Solar Cycle,” Mathew J. Owens et al., 2021 May 20, Solar Physics