Key Takeaways
- The recent geomagnetic storm provided spectacular aurora displays across the U.S.
- Wednesday evening was likely the final chance for most Americans to see the phenomenon
- The third and most energetic coronal mass ejection (CME) arrived Wednesday
- Auroras were visible from Alabama to northern California at peak activity
Americans who missed this week’s spectacular northern lights displays have likely lost their final opportunity, as forecasters confirm the geomagnetic storm activity has subsided. The dazzling auroras, which reached as far south as Florida on Tuesday, were unlikely to return after Wednesday evening.
The Space Weather Prediction Center confirmed Wednesday afternoon that the aurora could potentially be visible from Alabama to northern California. Forecasters noted the “final and most energetic CME” – meaning coronal mass ejection – had arrived that day.
What is a Coronal Mass Ejection?
A CME represents an eruption of massive clouds containing protons, electrons and magnetic fields from the sun’s outer atmosphere, traveling at extremely high speeds.
“This latest CME [has] arrived. It’s faster than the previous CMEs and our wind speeds have shot up over 800 kilometers (497 miles) per second,” Shawn Dahl, a forecaster at NOAA’s Space Weather Prediction Center in Boulder, Colorado, said in a video posted on X.
How Auroras Form
When these solar particles reach Earth’s magnetic field (the magnetosphere), they collide with particles surrounding our planet. This interaction produces the colorful light displays known as aurora borealis in the Northern Hemisphere and aurora australis in the Southern Hemisphere.
Storm Intensity Comparison
The third CME achieved a G3 rating with potential to reach G4 – the second-highest level on the five-step scale that previous CMEs had attained. According to Dahl, Tuesday’s magnetic activity measured “eight to 10 times stronger than normal background levels,” while Wednesday’s event was “about five times stronger so not as intense.”
