Aurora borealis in Ottawa: Here’s how to see it tonight, and why it happens

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Ottawa was treated to a dazzling display of northern lights on Thursday evening for the second time in a week, thanks to a severe geomagnetic storm.

The U.S. National Oceanic and Atmospheric Administration’s Space Weather Prediction Centre says severe geomagnetic storm conditions occurred across Canada and around the planet Thursday, caused by the latest in a number of coronal mass ejections from the sun in the last few months.

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It meant stunning displays of northern lights were observed from coast to coast across Canada, and as far south as Alabama.

Aurora borealis is expected to be visible again in a large part of North America on Friday night, according to NOAA forecasts.

Do you have photos of the aurora borealis over Ottawa? Send them in toonline@ottawacitizen.com and we’ll add some of them to our story.

What causes aurora borealis?

These geomagnetic storms are caused by solar particles which cause a disturbance in the Earth’s geomagnetic field.

Along with aurora borealis, also called northern lights, the storms can also potentially affect satellite communication, GPS, certain radio transmissions and power grids, the NOAA said Thursday.

This time, northern lights were seen further south than usual, due to the intensity of the storm.

A coronal mass ejection, like what’s causing this week’s aurora, is when the sun “flings out large amounts of solar material in the form of huge bubbles of charged particles (plasma) threaded with magnetic field lines,” according to the European Space Agency.

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What about the different colours?

In Ottawa, stunning blue, green, purple and red northern lights were seen across the city.

The National Weather Service in Indiana explained that atomic oxygen and altitude are what change the colour of aurora borealis. The particles released by the sun excite different atoms at different altitudes of the atmosphere, creating the light show.

Red aurora borealis is only visible under intense solar activity. It occurs at high altitudes, where the concentration of oxygen is lower, the weather office said. Whereas green lights appear at lower altitudes, where the concentration of oxygen is higher.

Blue and purple lights, meanwhile, can also be seen during intense solar activity. Those are caused by ionized molecular nitrogen, which is typically found at lower altitudes where atomic oxygen is less prevalent.

Where can you see them in Ottawa?

Due to light pollution, the best place to see aurora borealis is outside major city centres, though people posted photos on social media of stunning displays of aurora borealis across Ottawa on Thursday night.

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Using this light pollution map you can see where in the region you’ll have the best chance of seeing the lights.

Tips for safe sky-gazing

Ottawa Police are reminding people to stay safe on the road while looking skyward.

“Last night, many vehicles were observed driving very slowly (where it would be unexpected), veering all over the road, parking dangerously, and their lights turned off,” the police force said on social media Friday.

“The Northern Lights are an exceptional sight, but please prioritize road safety if you go out to see them. Let’s all enjoy the beauty of the sky while keeping our roads safe for everyone.”

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