Solar storm wanes after dazzling northern lights streak across the sky for back-to-back nights

Skygazers across the Northern Hemisphere were treated to a spectacular sight this week as vibrant northern lights illuminated the night sky following consecutive solar eruptions that sparked a rare, severe geomagnetic storm.

The solar phenomena-known as coronal mass ejections (CMEs)-weakened by Thursday after auroras became visible mainly across northern latitudes of the U.S. and Canada Wednesday night.

However, Tuesday’s display was especially breathtaking, with vivid green, red, purple and pink hues dancing overhead across much of the United States, reaching as far south as Florida, Texas and Georgia.

The AccuWeather map below highlights some of the most stunning images captured nationwide during the height of this week’s aurora activity.

The Severe (G4) geomagnetic storm reached level 4 out of 5 on the NOAA Space Weather Scales, just below the “extreme” (G5) threshold. The event was one of the strongest since May 2024, when the historic Gannon solar storm produced widespread auroras and satellite disruptions.

This week’s powerful solar activity also impacted space operations. Blue Origin delayed the second launch of its New Glenn rocket, which was scheduled to send two NASA satellites to Mars on Wednesday. NASA postponed the liftoff due to the potential for increased atmospheric drag and other effects on spacecraft caused by heightened geomagnetic activity.

What caused this week’s northern lights show?

According to the NOAA Space Weather Prediction Center (SWPC), the sun unleashed an X5.1-class solar flare earlier in the week, temporarily disrupting high-frequency radio communications.

The flare was followed by multiple CMEs, with two striking Earth on Tuesday and generating the G4 geomagnetic storm responsible for widespread aurora sightings.

“We had two of three CMEs arrive here last night, and they arrived at Earth with a pretty darn good punch-enough to warrant the G4, the severe storm levels that we did, in fact, achieve,” said Shawn Dahl, SWPC Service Coordinator, in a video update Wednesday night. “A lot of the country got to see the aurora, those northern lights last night.”

A third CME arrived Wednesday, but it was weaker and less magnetically aligned with Earth, resulting in reduced aurora activity compared to the night before.

“Yesterday’s activity was eight to 10 times stronger than normal background levels for a magnetic field. This one is about five times stronger, so not as intense,” Dahl said. “Right now, the magnetic field is aligned with Earth’s, which is not favorable for heightened geomagnetic storm activity-but it can shift at any time.”

How solar storms create auroras

CMEs are the primary drivers of intense aurora events. When billions of charged particles from the sun collide with Earth’s magnetic field, the energy released excites gases in the upper atmosphere. These reactions produce glowing light displays-typically green, pink, red or blue-depending on which atmospheric gases are involved and the altitude of the interaction.

The SWPC measures geomagnetic disturbance using the Planetary K Index (Kp index), which ranges from 0 to 9. On Tuesday, the index spiked to 8.67, just below the highest level. A Kp 9 would indicate an event capable of producing auroras visible near the equator.

That intensity explains why so many people across North America were able to witness Tuesday night’s remarkable aurora display.