Skywatchers across Canada could be treated to a dazzling light show overnight Tuesday and Wednesday, owing to a pair of solar belches that cast a cloud of magnetized gas into space, triggering a strong geomagnetic storm.

The U.S. National Oceanic and Atmospheric Administration's Space Weather Prediction Center observed a "severe" G4 geomagnetic storm Tuesday morning around 9:58 a.m. ET.

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Swirls of green and red appear in an aurora over Whitehorse, Yukon in this NASA handout image. A 'severe' G4 electromagnetic storm set off by bursts of magnetized gases from the sun is expected to bring northern lights over much of Canada and as far south as northern California over the next two days. (Courtesy of David Cartier, Sr./NASA)

"That means the particle environment around the Earth is going to be quite disturbed, and that might mean that you'll see a lot of aurora as the night falls," said Emma Spanswick, associate director of the Auroral Imaging Group at the University of Calgary.

AuroraMAX, the public outreach initiative dedicated to the science of the northern lights, issued an alert for "active auroras" on March 17 and 18, flagging observers in Yukon, Northwest Territories, Alberta, Saskatchewan, Manitoba and parts of B.C., Ontario, Quebec and Newfoundland and Labrador.

NOAA said the G4 solar storm was the result of two coronoal mass ejections, or CMEs, observed leaving the sun on March 15.

The auroras are expected to streak across the skies tonight and tomorrow.

Disruptions to GPS, power

"It takes a long time for the actual particles ejected to reach the Earth. That's why we have trouble predicting it," Spanswick said. "We're never sure when it's going to hit. It might miss us because it's got days to travel."

CMEs occur when the sun sporadically releases cloudy blobs of gas and magnetic field lines.

Northern Lights

Geomagnetic storms are caused by charged particles in the solar plasma interacting with the Earth's magnetic field. That excites nitrogen and oxygen in the Earth's upper atmosphere, sometimes generating northern lights or auroras. (Duk Han Lee/CBC)

The currents produced in space could disrupt spacecraft operations, GPS systems and cause electrical power outages.

In past G4 electromagnetic storm events, Spanswick said the auroras have moved as far south as northern California.

In a space weather alert, NOAA said auroras may be seen as far south as Pennyslvania, Iowa and Oregon.

Toronto area residents may also catch a glimpse, too. "But you've got to get somewhere dark," Spanswick said, adding she can't recall the last time a G4 scale storm occurred.

The northern lights become visible when charged particles spat out by the sun collide with Earth's magnetic field.

Although it will be partly cloudy this evening over Yellowknife, a live stream of the northern lights from the Northwest Territories capital can be accessed on the AuroraMAX website. The project is a partnership between the University of Calgary, the City of Yellowknife, Astronomy North and the Canadian Space Agency.