A hyperactive sunspot region fires its fourth eruption toward Earth in four days

A sunspot cluster designated AR4549 has thrown off four coronal mass ejections toward Earth since Monday, prompting NOAA's Space Weather Prediction Center to revise its storm forecast repeatedly through the week. The latest guidance, issued Friday afternoon, calls for a minor geomagnetic storm overnight and into Saturday, with a stronger one now expected Sunday as the agency continues to track how the eruptions are lining up on their way across 93 million miles of space.

The region has been one of the more active patches on the sun's Earth-facing hemisphere all week. It first drew attention Monday with a moderate, M1.4-class solar flare and an accompanying ejection that forecasters at Belgium's Solar Influences Data Analysis Center clocked at roughly 560 kilometers per second. NOAA's own radio-burst monitoring put a similar early-week ejection near 950 kilometers per second. That eruption prompted the agency's first watch for a moderate, G2-category storm on Friday, Oct. 9.

The numbers behind the forecast

The region did not let up. On Thursday it produced a much stronger M6.7-class flare, peaking at 11:48 a.m. EDT and briefly degrading high-frequency radio communication on the sunlit side of Earth, a disturbance NOAA rated R2, or "moderate," on its radio-blackout scale. A radio instrument at the agency's Sagamore Hill site in Massachusetts recorded a Type II burst, the signature of a shock wave racing ahead of a new ejection, with a provisional velocity near 4,125 kilometers per second — among the fastest such readings NOAA has logged from this stretch of the solar cycle, though the figure describes the leading shock rather than the bulk of the ejected plasma, which typically trails it.

That eruption was the fourth earth-directed CME traced back to AR4549 in four days, and forecasters said at the time that it could conceivably catch up with and merge with the third, already en route. The result has been a forecast that has moved almost daily:

• Monday, Oct. 6: First G2 (moderate) watch issued, for Friday, Oct. 9.
• Thursday, Oct. 8: A fourth CME launches behind an M6.7 flare rated R2 for radio blackout.
• Friday morning, Oct. 9: NOAA's watch shifts the moderate storm risk to Sunday, Oct. 11, with little elevated activity expected Saturday.
• Friday afternoon, Oct. 9: The watch is revised again, calling for only a minor (G1) storm Friday night and Saturday, with the moderate (G2) threshold now pegged to Sunday.

Under G2 conditions, aurora has historically been reported as far south as New York and Idaho, according to NOAA's own scale descriptions, though forecasters caution that how far south the lights actually reach depends on the orientation of each ejection's magnetic field when it arrives, something that cannot be measured precisely until the material is close to Earth.

A sun that has stayed stubbornly active

The run of eruptions comes roughly two years after NASA and NOAA jointly announced that the sun had entered the maximum phase of Solar Cycle 25, the roughly 11-year rhythm of rising and falling sunspot activity that drives space weather. Officials were careful at the time to note that declaring a maximum phase said nothing about whether the single most intense event of the cycle had already happened.

"This announcement doesn't mean that this is the peak of solar activity we'll see this solar cycle," said Elsayed Talaat, director of space weather operations at NOAA, when the maximum phase was declared in October 2024.

That caution has held up. Space.com's own survey of solar activity notes that the most intense flares and ejections of a cycle have historically tended to arrive during its declining phase, sometimes years after the formal maximum, rather than at the peak itself. AR4549's week of repeated eruptions is consistent with a sun that remains well above the unusually weak activity some forecasters had projected for this point in the cycle.

Who notices, and who does not

For most people, a G1-to-G2 storm is a non-event. The practical effects described in NOAA's advisories are modest: brief voltage fluctuations on high-latitude power grids, minor orientation and drag issues for satellites in low Earth orbit, and the kind of HF radio fade that mainly concerns aviation, shipping and amateur radio operators working near the poles. The M6.7 flare's radio blackout, while rated moderate, lasted only tens of minutes and was centered on the side of Earth facing the sun at the time.

The more visible effect is the one skywatchers care about. Space.com's coverage through the week has tracked the shifting odds for northern-tier states, from Washington and Montana through the Great Lakes and into northern New England and New York, as well as much of Canada and Alaska. Updated reporting Friday noted that with multiple ejections converging in quick succession, there remains real uncertainty about how far south any display might reach, and that the picture could still improve or fade depending on exactly how the incoming material strikes Earth's magnetic field.

What happens next

NOAA typically refines its CME arrival estimates as spacecraft-based coronagraph images come in over the following day or two, which is why the agency's watches for this event have already been reissued three times since Monday. The next scheduled update was expected Friday evening, ahead of the window forecasters are now watching most closely: Saturday night into Sunday, when the moderate, G2-level storm is currently predicted.

AR4549 remains on the Earth-facing side of the sun for a few more days before the sun's rotation carries it out of view, and forecasters have not ruled out further flares from the region in the meantime. For now, NOAA and independent aurora forecasters are advising anyone at higher latitudes who wants a chance at seeing the lights to check updated forecasts close to nightfall rather than relying on guidance issued a day or more in advance, given how much the numbers have already moved this week.