The same active region of the sun that produced stunning auroras that were visible as far south as Mexico earlier this week has erupted again.
On Friday the sun released a powerful, X4.0-class solar flare—a parting blow from the dynamic active region 4274 (AR4274), which is rotating toward the far side of our star. Solar flares are ranked by strength, with X-class flares being the most powerful.
Following the flare came a coronal mass ejection (CME), which is when the sun shoots out blobs of solar plasma and magnetic field that—if they reach Earth—can interact with our planet’s atmosphere, triggering auroras. It’s unclear whether today’s outburst will hit Earth—CMEs travel at varying speeds, with some taking days to cross the distance between the sun and our planet.
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According to the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center, it is possible that northern parts of the contiguous U.S. could see auroras on Friday evening.
Although AR4274 will be unable to impact Earth on the sun’s far side, the star’s approximately 27-day spin may carry the active region back within firing range.
This week’s outbursts were not out of the ordinary for the sun, which is currently around the peak of its 11-year solar cycle of activity.
The exact times of solar maximum—and its opposite, solar minimum—are generally determined months after the fact and are based exclusively on the number of sunspots visible on our star. Powerful solar outbursts, however, often continue throughout the initial years of the declining phase of the activity cycle.