Sunspot behind historic auroras and solar storm returns for more displays

The sunspot group AR3664, which caused the remarkable May 2024 solar storms and widespread auroras is back—well, almost.

Yesterday (May 27), a potent X-class solar flare erupted from the sun’s southeastern limb, reaching its peak around 3:08 a.m. EDT (07:08 GMT), according to

Solar storm back, sunspot group AR3664 could bring more auroras

The NOAA’s Space Weather Prediction Center registered a flare off the southeast limb of the sun measuring X2.8. X-flares represent the strongest classification of flares, although we witnessed several more powerful flares earlier this month. The higher the number, the greater the intensity of the flare, which can lead to radio and other communication blackouts on Earth.

Credit: NASA

The source of the May 10 solar superstorm, which produced auroras visible in all fifty states for the first time in decades, was also sunspot AR3664. During early May, it was more directly aimed at Earth. Similar to Earth, the sun rotates on its axis, and sunspot AR3664 has spent the past few weeks on the far side of the sun, away from our planet. However, it is now rotating back into view from our vantage point.

It seems AR3664 still has some activity left, and AR3691 is also growing with X-flare potential. This could lead to a repeat of the May 10 event in the next week or two. No official forecasts yet, but the sun’s behavior is unpredictable. Monday’s X-flare hints at more excitement ahead, especially considering we’re still some time away from the solar cycle’s peak in activity.

Solar flares vs. CMEs: Understanding their impact on Earth

The strength of a solar flare is just one factor in how solar activity impacts Earth. While solar flares release bursts of electromagnetic radiation from the sun’s surface due to the release of built-up magnetic energy, the effects on our planet, such as auroras and disruptions to electrical systems, are more closely tied to coronal mass ejections (CMEs).

These are eruptions of charged particles that can take several days to reach Earth and have directionality. When a CME originates from a sunspot more directly aimed at Earth, it’s more likely to cause significant impacts.

Solar flares are categorized by size, with X-class flares being the most powerful. Each class is further defined by numbers from 1 to 10 (and even beyond for X-class flares) to indicate a flare’s relative strength. According to, the recent X-flare measured at X-2.9.