Millions of people around the world were dazzled by the aurora borealis in mid-May — "possibly one of the strongest displays of auroras on record in the past 500 years," according to NASA.
Now, the huge, still-active sunspot region responsible for the multi-day auroral displays is rotating back into view of Earth. Between about June 4 and 6, it will be in perfect alignment to affect us again, according to Ryan French, a researcher at the National Solar Observatory who investigates solar flares.
"The region is clearly still capable of producing X-class flare events," the most powerful kind, French says. In fact, it did just that on Memorial Day, and again today, May 29. (See below for video of today's activity.) "But the question is whether it can do so with the same magnitude and frequency as it did earlier this month."
After the sunspot region unleashed its barrage of solar storms in mid-May, lighting up the nighttime skies and dazzling viewers much farther south and north than usual, it rotated out of sight and settled down a bit. Although it was still active, it produced fewer large flares and eruptions, and it is still relatively better behaved right now, according to French.
What can we expect moving forward? I posed that and several other questions to French in a couple of emails. Here's our back-and-forth, in Q&A format (with very minor editing for clarity and brevity):
Q: Do we know yet whether this sunspot region will be capable of producing something akin to mid-May’s geomagnetic activity? If not, how long might it take to know?
A: To accurately assess the complexity of the active region, and its flaring potential, we need measurements of the sunspot magnetic field. This is very difficult to do near the edge of the Sun, so we must wait one to two more days to get an accurate diagnostic for this. When these measurements come in, we'll be better able to model the flare potential of the region. Although large flares are currently less frequent, it only takes one well-placed eruption to create a strong northern lights show.
Q: Do we have any ideas of the odds?
A: For the next three days, the NOAA Space Weather Prediction Center has issued a daily 30% chance of an X-class solar flare, and 60% chance of an M-class. (Newest forecast here, updating every 12 hours).
To get a decent aurora show at Earth, there are more variables than just the flare size. We'd need a solar flare to trigger a large eruption with 1) high density and velocity, 2) a favourable magnetic orientation relative to Earth's magnetic field. 3) a source region pointed at us. Not all flares trigger this kind of eruption.
Q: What would the timing be? First week of June? Can we say with any further accuracy?
A: For the best chance of aurora, a solar eruption needs to erupt from a region magnetically-connected with Earth (meaning it comes our way). This Sun-Earth connection is best for eruptions just right of Sun center. Eruptions slightly left of center can still reach us, but eruptions too close to the edge of the Sun are unlikely to head our way.
The May 2024 solar storms were created by a succession of multiple, near perfectly-placed eruptions. With the Sun's rotation period of around 27 days, the sunspot region will be in this perfect placement again for a few days from June 4-6th. To cause a strong solar storm at Earth, we'd need a suitable eruption occurring close to this window.
Q: Any other insights you may have about this would be greatly appreciated.
A: As we approach peak solar activity in 2024-2025 (at least for the next 11 years), the chances of strong solar flares and associated solar storms are higher. However, the size of the May 2024 solar storm event is somewhat rare, last happening in 2003. [Note: This is different than the strength and spread of the aurora themselves.] Although it's possible we'll see another G5 geomagnetic storm this year, it's also very possible we won't get another show like that again for quite some time.
But even if near-future events don't create aurora quite as far south, millions of people at northern latitudes will definitely still get more chances to spot them this year.
