Severe geomagnetic storm may spark widespread auroras over Canada on Friday
Widespread auroras are possible across most of Canada and a large swath of the U.S. on Friday night as forecasters expect a potent geomagnetic storm to kick off the weekend.
This event ranks as a ‘severe’ G4 on the scale used to measure the intensity of geomagnetic storms. The scale ranges from from G1 (minor) on the low end to G5 (extreme) on the high end.
Forecasters with NOAA’s Space Weather Prediction Center (SWPC) issued a geomagnetic storm watch ahead of the event, saying on Friday that “watches at this level are very rare.” This is the first G4-level watch issued by the agency since January 2005.
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Expected to arrive late Friday night
Our weekend aurora potential is the result of three separate coronal mass ejections (CMEs) merging into one as they approach Earth. A CME is a burst of plasma and magnetic field released from the Sun’s blazing hot outer atmosphere.
The charged particles of a CME can filter into Earth’s upper atmosphere around the magnetic poles, ionizing gasses like oxygen and hydrogen to create the phenomenal display of dancing colours we see as the northern lights.
The SWPC expects the geomagnetic storm to peak late Friday night into very early Saturday morning, with the strongest aurora potential around 11:00 p.m. to 2:00 a.m. Eastern Time, or 8:00 p.m. to 11:00 p.m. Pacific Time.
If the expected timing holds up, folks in B.C. might struggle to see subtler colours given that sunset isn’t until after 8:30 p.m. for many communities.
Any change in this geomagnetic storm’s arrival time would affect Canada’s viewing. An earlier arrival might favour Europe over Canada, while a later arrival might allow for more widespread viewing opportunities across the country.
A geomagnetic storm of this caliber could produce visible auroras far south of the border, as well. NOAA says that the northern lights could be visible as far south as Alabama and northern California if the event peaks at the right time.
Clouds may obscure the view for some regions
Sunlight is only part of the equation when it comes to spotting the northern lights. Where might clouds obscure the view?
The latest forecast for Friday night paints a mixed picture across the country. Cloud cover may obscure the view for parts of the East Coast, including for folks in St. John’s and Halifax.
A decent chance for plenty of clear skies could allow fantastic viewing for a wide swath of Quebec, including the Montreal area, as well as much of southern Ontario. You’ll want to get away from the bright lights of the Greater Toronto Area’s for the best chance at seeing colours dance in the night sky.
Farther west, aurora watchers may find luck between patchy clouds expected to blanket northern Ontario and portions of Manitoba.
The best opportunity for clear skies exists on the western Prairies and into British Columbia. Folks around Regina, Saskatoon, Edmonton, and Calgary may catch a good show if this geomagnetic storm lives up to its full potential. Clear skies throughout B.C. may offer a good view if the northern lights arrive after sunset and twilight.
Aurora potential increases as solar maximum arrives
We’re approaching the maximum of Solar Cycle 25, a period during which solar flare and sunspot activity increases—along with more opportunities for CMEs that may produce auroras.
Experts rate the intensity of geomagnetic activity on the Kp Index, which ranges from Kp 0 on the low end to Kp 9 on the high end. Values around Kp 7 are sufficient for nationwide aurora visibility.
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Several geomagnetic storms since late last year have produced widely viewed auroras in the Northern Hemisphere, including a G3 (strong) storm in November that made the northern lights visible as far south as Virginia and Ukraine.
Auroras aren’t the only effects of a geomagnetic storm. The surge of charged particles into the atmosphere can cause radio blackouts and GPS disruptions. The strongest geomagnetic storms can even threaten power grids.