'I saw colours I'd never seen before': Aurora borealis lights up Alberta skies

If you were outside and looked up Monday night, you likely witnessed one of Mother Nature's most spectacular displays.

The aurora borealis, or northern lights, put on a dazzling show that was visible from within the city and filled the night sky with vibrant colours.

Chris Ratzlaff, an aurora chaser from Airdrie, Alta., didn't have to go far to catch the celestial spectacle, this time.

"I just went on my deck," he said.

"The event last night was so bright that people were seeing it from downtown Calgary."

David Knudsen, head of the physics and astronomy department at the University of Calgary, explained that the intense display was caused by a coronal mass ejection (CME) from the sun.

"Occasionally, the sun gets active and it spits out a blob of material known as plasma, a CME," Knudsen said.

"That's what happened Monday – a big blob of magnetically charged plasma hit the Earth."

Ratzlaff said he was thrilled to share the experience with others.

"I texted my neighbours to get outside right now," he said.

"And there were a lot of people outside that were like, 'Wow, it was amazing.'"

Ratzlaff moderates a Facebook group called Alberta Aurora Chasers, which monitors space weather to predict when and where the northern lights can best be seen.

It can be found here.

Photographer Matt Melnyk, who has been capturing auroras for 17 years, said Monday's display was the best he had ever seen.

"I saw colours I'd never seen before," he said.

"I saw orange, I saw yellow, I saw pinks and I saw bright red to the naked eye."

Melnyk went to a dark spot in the countryside to capture his images but the aurora was so intense that it was still visible even under Calgary's canopy of light.

"It was phenomenal," said Nicko Lineras, a Calgarian who witnessed the display.

"Like the red lights in the sky, and I've never seen it just encompassing the whole sky."

Solar flares and CMEs wax and wane on an 11-year cycle.

"We are right at the peak of that cycle right now," Knudsen said.

"And it's going to stay good for all winter, and maybe even into next winter."

Knudsen added that the intensity of auroras depends on the density and speed of the CME, as well as its magnetic field.

"We really don't know they're going to hit the Earth until they actually arrive. A lot of people went out on the weekend looking for auroras Saturday night," he said.

"Turns out, the blob hit the Earth but the magnetic field was in the wrong direction."