A powerful M5.7 solar flare erupted from the sun on May 10 and sent a coronal mass ejection racing outward that could still give Earth a glancing blow later this week. The flare peaked at 9:39 a.m. EDT, or 1339 GMT, and came from sunspot region AR4436 as it turned into Earth’s strike zone on the sun’s northeastern limb.

The eruption also triggered a radio blackout over the Atlantic Ocean, a reminder that strong solar activity can have immediate effects on the planet below. These blackouts happen when intense X-ray and ultraviolet radiation from solar flares ionize Earth’s upper atmosphere, disrupting high-frequency radio signals used by aviators, mariners and amateur radio operators.

Forecasters at NOAA’s Space Weather Prediction Center and the U.K. Met Office say part of the expanding plume of solar material may still brush past Earth around early May 13. If it does, the impact is expected to be weak but could still produce minor geomagnetic storm conditions later this week.

That forecast matters because the sun is not done yet. NOAA and the U.K. Met Office say there is a chance for additional M flares and even X-class eruptions in the coming days as sunspot regions AR4436 and AR4432 continue to evolve.

Solar flares are ranked A, B, C, M and X, with each step representing a tenfold increase in energy output, and X-class events are the most powerful. The May 10 eruption falls well below the scale of the extreme storm Earth saw in May 2024, when the first G5 geomagnetic storm since 2003 produced auroras far beyond usual high-latitude ranges, including over southern Florida and Mexico. This event may still scrape the planet, but it is not expected to come close to that level.

The answer to the question hanging over this flare is straightforward: Earth is likely to get only a glancing hit, if any, and the biggest effect may be brief radio disruption rather than a major geomagnetic storm.