The glow of the aurora borealis, or northern lights, is seen in the horizon in the Kawartha Lakes region, southern Ontario, Canada, in February. Reuters

American astronaut Scott Kelly probably thought he’d seen everything there is to see from 251 miles above Earth’s surface, until he spotted a rare and spectacular phenomenon: The aurora borealis, which typically shines green, was bright red. The aurora, commonly known as the northern lights, was the result of a major solar storm that bombarded Earth with magnetic plasma on Monday. It was potentially the largest solar storm to hit the planet since September 2005, according to scientists.

Kelly shared images of the red aurora borealis via his Twitter account. “I've never seen this before -- red aurora,” Kelly tweeted Monday. “Spectacular!” Kelly, who is about three months into his yearlong stay aboard the International Space Station, noticed the aurora borealis while he was zooming over Russia.

The aurora borealis occurs over the North Magnetic Pole and is the result of highly charged electrons colliding and reacting with Earth’s atmosphere. The awe-inspiring colors produced by the cosmic pileup are the result of the electrons reacting with oxygen, nitrogen and other atmospheric elements.

Low-altitude collisions between electrons and the atmosphere result in the yellow-green color commonly spotted during northern lights events, according to CBS News. Rarer red auroras occur when the electrons strike oxygen atoms at higher altitudes.

“What happens in an aurora is similar to what happens in the neon lights we see on many business signs,” reports. “Electricity is used to excite the atoms in the neon gas within the glass tubes of a neon sign. That’s why these signs give off their brilliant colors. The aurora works on the same principle – but at a far more vast scale.”

People across the U.S. and Canada were treated to the display Monday night. "They were visible in deep twilight!" one witness, Chris Cook, told from Cape Cod in Massachusetts. "I positioned myself on a beach overlooking Cape Cod Bay so I could capture the reflection in the water at low tide."