Beautiful northern lights are expected to put on a show across Canada tonight, even in the South, thanks to the double impact from solar plasma hitting the Earth.
The combined effect "should light up the skies pretty good over Canada," predicted William Murtagh, program co-ordinator for the NOAA Space Weather Prediction Center in Boulder, Colo.
But it could also cause some GPS, electrical grid and radio disruptions.
The latest update from the Space Weather Prediction Center, posted at 9:15 p.m. ET Thursday, recommends that aurora watchers look for possible activity Friday night through Saturday night, as far south as New York, Wisconsin and Washington state. More detailed information is available from the centre's Ovation aurora prediction tool.
Two eruptions from solar storms earlier this week blasted plasma from the surface of the sun toward the Earth – a phenomenon known as a coronal mass ejection or CME.
The first blast, which was smaller, hit the Earth Thursday night, generating a small geomagnetic storm in the atmosphere, the Space Weather Prediction Center reported. Such 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 — beautiful moving curtains of red and green light in the night sky.
Murtagh told CBC News that he saw some photos of auroras spotted Thursday night in Minnesota. But more impressive ones were expected Friday night.
That's because the second blast — from a powerful X-class flare — is scheduled to smack the Earth Friday, and its effect will combine with that of the previous storm.
"It always gets our attention just that little bit more, when we see two or more," Murtagh said. "But if you've got another coming right behind this, it prolongs the storm and the dynamics can be such that the second impacts can be quite strong."
The geomagnetic storm level tonight is expected to hit level 3, classified as strong, on a scale of 1 to 5, where 5 is the highest. At northern latitudes, it may even hit level 4 — severe — Murtagh suggests.
The last time we saw this intensity level in a geomagnetic storm was in June 2013, despite the fact that we are at the peak of the sun's 11-year solar cycle.
Risk to power grids
Besides generating beautiful auroras, such storms can damage power infrastructure — a series of powerful solar storms in October 2003 damaged power grids in both Europe and Africa, Murtagh noted.
Power grid operators have already been warned about this week's storms and are taking precautions.
"It's very manageable," Murtagh said.
He added that GPS navigation may also be disrupted, along with compass readings, but hikers and geocaching enthusiasts need not worry, as the problems shouldn’t last very long.
"It just may be a bit of a nuisance."
The disruptions may be more of a problem for GPS users like the mining industry who take continuous measurements rather than intermittent readings.
The storm may also cause problems in getting satellites oriented the right way, and may cause high-frequency radio disruptions in northern latitudes.
While an event like this hasn't happened in more than a year, Murtagh noted that in the long term, solar flares like the ones that erupted this week aren't that unusual. They typically happen 100 times over each 11-year solar cycle, although only a small number of them are aimed at the Earth.
In any case, that's in the long term, he said. Even though we're at the peak of the current solar cycle, this cycle has been "unusually quiet," he added, "so we haven't seen too many of these."
Given that, you might want to take advantage the show this weekend.