Sun's most active sunspot fires five flares, raising aurora and radio-blackout watch

A sunspot region that has been simmering for more than a week erupted into sustained activity Tuesday, firing five M-class solar flares — the second-strongest category tracked by space weather forecasters — with the largest peaking at M7 magnitude at 10:02 UTC, according to tracking by EarthSky and independent solar observers, corroborated by the NOAA Space Weather Prediction Center's daily activity summary.

The region, designated AR4513, had been rotating into better view of Earth-facing instruments after a relatively quiet stretch, and researchers say it produced all 16 of the day's flares recorded across the visible solar disk, a level of concentrated activity that surprised some forecasters after several calmer days.

A glancing blow expected this week

The strongest of the eruptions triggered a moderate, R2-level radio blackout over parts of Africa, temporarily degrading high-frequency radio communications in the affected region — a routine but disruptive side effect of strong solar flares that primarily affects aviation and maritime communications on the sunlit side of the planet at the time of the eruption.

More consequential for skywatchers is the coronal mass ejection, or CME, associated with the flare activity. Forecasters at Space.com and allied space-weather services say a glancing blow from the ejected material could reach Earth's magnetic field around Aug. 28, potentially triggering a minor to moderate geomagnetic storm. If the timing holds, aurora watchers as far south as the northern tier of the United States — including areas around Seattle and Minneapolis — along with northern Canada, Scotland and Scandinavia could see displays of the northern lights over the coming nights.

Solar physicists caution that CME forecasting remains imprecise even days out, since the exact trajectory, speed and magnetic orientation of the ejected plasma determine how strongly — or whether — it interacts with Earth's magnetosphere. A glancing hit could produce only modest aurora activity confined to far-northern latitudes, while a more direct impact could push the aurora oval further south and raise the risk of further radio and GPS disruptions.

AR4513 has been one of the more prolific active regions of the current solar cycle's declining phase, having already produced an M8.1 flare earlier this month. Its continued activity underscores that although the sun has passed the peak of Solar Cycle 25, individual active regions can still generate significant space weather events as they rotate across the solar disk. NOAA's Space Weather Prediction Center is continuing to monitor the region as it moves toward the center of the solar disk, the position from which any future eruptions would be most likely to send material directly toward Earth.

For most people on the ground, the practical effects of this week's activity are limited to a possible aurora show and brief radio disruptions; satellite operators and airlines routing polar flights are the groups most likely to adjust operations in response to continued flare activity from the region. M-class flares, one step below the most powerful X-class category, occur regularly during active phases of the roughly 11-year solar cycle and rarely pose a direct hazard to people on the ground, since Earth's atmosphere and magnetic field absorb the bulk of the associated radiation.