Solar flares cause spectacular aurora borealis in Alaska skies

A series of solar flares, essentially explosions on the surface of the sun, caused unusually bright and colorful displays of aurora borealis in Alaska and other northern latitudes on Tuesday night.

University of Alaska Fairbanks Physics Professor Mark Conde said he and other researchers expect that atmospheric activity will continue to result in vividly colored displays of aurora, or northern lights, through Wednesday night. He described seeing large, tall swaths of red in the night sky from his home in Fairbanks.

“It was like seeing the fine wine of the aurora,” Conde said. “Deep red aurora is quite unusual, and they only really occur during extreme events like this.”

Aurora borealis is caused by charged particles, mainly protons and electrons, that stream into the Earth’s magnetic field and strike our atmosphere. The reaction essentially paints a picture on the atmosphere that is visible in the night sky.

Recent explosions on the surface of the sun have resulted in highly visible displays of northern lights because those solar flares caused more charged particles to come into contact with the Earth’s atmosphere.

Conde said that as solar winds stream by our atmosphere, they generate electric fields. The Earth’s magnetic field generally deflects particles away from the near-Earth region, but if the solar wind has an opposite magnetic charge, then it can penetrate into the protective bubble of the Earth’s magnetic field, and eventually find its way down to our atmosphere. He said that results in highly visible auroras like what was observable in many parts of the northern hemisphere last night.

“It’s almost like a switch,” he said of the favorably aligned magnetic fields. “(The solar wind) can open the switch and let itself in. And that’s kind of what happened last night, when (the cloud of materials from the solar flare) first hit the magnetic field it was extremely favorable to allow the solar wind to penetrate into the near-Earth environment and pump up the magnetosphere and produce the displays that we saw.”

He said the unusual deep red color of the displays was caused by a large flow of low energy particles that were able to interact with the Earth’s atmosphere.

Many people are drawn to the spectacular visuals of the aurora, but Conde said scientists study it for a more practical reason: The aurora is one aspect of space weather, which has significant effects on modern technology, including satellites and radio communication.

Conde said he and his colleagues have not yet heard of any big disruptions from this week’s solar flares, but they did disrupt data collection on two spacecraft that university researchers use to monitor the solar wind. He said in past years, solar winds have knocked Starlink internet communication satellites out of orbit, causing them to re-enter Earth’s atmosphere.

The solar flares that are causing such vivid auroras this week can also accelerate radiation that can be harmful to astronauts and spacecraft, Conde said.

“If there was an astronaut standing on the surface of the Moon last night — outside the magnetic, protective bubble of the earth — or en route to Mars, they wouldn’t have been killed, I don’t think, by the radiation, but there would have been enough radiation that they would have had significant health risks,” he said.

Another practical reason for a physicist such as Conde to observe the aurora is that the near-Earth environment is regarded by scientists as a natural laboratory.

“We can look at plasma phenomena occurring in space that we can’t possibly reproduce on Earth because… if you wanted to study those plasma interactions on the ground, you would need a vacuum chamber that would be 100 kilometers in diameter or something,” he said.

He said observations of how Earth interacts with solar wind and the near-Earth environment can help answer questions about the long term evolution of our upper atmosphere.

“Plus,” he said, “It’s pretty!”