Second round of Northern Lights possible across Canada tonight
The auroras may have bailed on us last night, but there's another chance to see them tonight!
If you have reasonably clear skies tonight, turn your gaze to the north for another chance to spot the Northern Lights.
In the wake of two massive eruptions from the Sun that swept past Earth late on Tuesday, displays of the Aurora Borealis were sparked in the skies above parts of Canada. Unfortunately, due to the exact conditions of the solar storms and how they affected Earth's geomagnetic field, the brightest auroras were delayed, causing them to skip over Canada almost entirely.
However, according to NOAA's Space Weather Prediction Center, the impacts of these solar storms have persisted throughout the day on Wednesday. Geomagnetic storm levels even reached the G4 (severe) category late in the afternoon. This gives us another chance at seeing auroras in the sky on Wednesday night.
SWPC forecasters are expecting G3 (strong) geomagnetic storm conditions in the early evening hours tonight, EDT. Following that, G1 (minor) storm conditions could persist as night falls across Canada.
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The Canadian Space Weather Forecast Centre is also predicting the potential for auroras tonight. All regions — polar, auroral, and sub-auroral — have been active to stormy throughout the day today. Their latest forecasts are calling for this to continue, with stormy conditions (equivalent to G1-G2 on NOAA's scale) possible through the night.
Will we see the auroras?
Simply due to the path the 'aurora oval' traces across the map of Canada, the viewing potential for the Northern Lights is almost always better in the western half of the country.
However, if stronger geomagnetic storm conditions persist as night falls across eastern Canada, auroras may push significantly farther south. The oval could even pass over the Southern Townships and the Lower Great Lakes, including southwestern Ontario.
Having at least reasonably clear skies is essential for seeing the auroras, though. Here are the cloud conditions forecast for eastern and western Canada overnight.
The best areas of the country to view the Northern Lights tonight are across Ontario, parts of southern Saskatchewan, central Alberta, and southern British Columbia.
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What's going on?
The two solar storms that swept past Earth overnight on Tuesday were the result of two large 'filaments' on the surface of the Sun.
Due to the Sun's magnetic fields, massive arcs of solar plasma can stretch for immense distances across its surface. When these arcs are seen along the edge of the Sun, they are called prominences. When they are viewed against the brighter surface of the Sun, though, they are known as dark filaments.
Two images of the Sun from August 31, 2012, taken by the Solar Dynamics Observatory show prominences and filaments, one of which erupts from the lower left region of the Sun, becoming a coronal mass ejection or 'solar storm'. (NASA SVS/Scott Sutherland)
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Some filaments can have a very tenuous connection to the Sun's surface, and even the smallest disturbance can cause them to tear away and launch into space.
That is what happened Sunday morning, as seen below via NASA's Solar Dynamics Observatory.
The first filament eruption (top row) shows the filament just before (top left), and the 'canyon of fire' splitting open in the wake of the eruption (top centre and top right), which sends the filament as a CME towards the lower left of the view. The second filament (bottom row) erupts towards the lower right, as another 'canyon of fire' expands away from the eruption point. (NASA SDO/Scott Sutherland)
As the two filaments expanded out into space, one was headed slightly ahead of Earth, while the other was aimed slightly behind. Both were expected to make glancing blows on Earth's geomagnetic field as they swept by.
When these two solar storms arrived, they caused a spike in the amount of solar particles flowing past the planet. However, this did not immediately result in bright aurora displays.
According to NOAA SWPC, the magnetic fields of the two storms had a complex interaction with Earth's geomagnetic field.
The real-time solar wind measurements from the ACE and DSCOVR satellites shows the magnetic properties of the coronal mass ejections (bright blue line, top of graph) and the response by the auroras (inset images, below). (NOAA SWPC/Scott Sutherland)
As shown in the graph above, one of the conditions space weather forecasters pay attention to is the direction of the solar wind magnetic field (the bright blue line, Bz), which includes the influence of passing solar storms. The strongest geomagnetic impacts, and thus the brightest aurora displays, occur when the solar wind magnetic field has negative polarity (opposite to the polarity of Earth's geomagnetic field). That occurs when the bright blue line dips below the grey 'zero' line of that part of the graph display.
This played out overnight on Tuesday in three stages, as shown. With the initial arrival of the CMEs (outlined in purple), a minor aurora display resulted, as the magnetic field of the solar storms flipped back and forth between negative and positive polarity. Aurora activity then damped down (outlined in green) as the magnetic field went positive for much of the night, and then a major burst of the auroras occurred after sunrise (orange), as the magnetic field direction flipped negative again and stayed there.
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When the solar wind/CME magnetic field was positive, thus matching the polarity of Earth's geomagnetic field, the two fields pushed against one another. This caused the solar particles to flow around us with little to no auroras evident during that time. However, when the solar wind/CME magnetic field flipped negative, it formed connections with Earth's geomagnetic field, allowing high-energy particles from the flow to more easily stream down into Earth's atmosphere.
With the solar wind/CME magnetic field so consistently negative throughout the day on Wednesday, these conditions could persist into the night, thus potentially resulting in strong displays of the Aurora Borealis.
With files from The Weather Network. Thumbnail image taken by Stormhunter Mark Robinson from near Guelph on the night of September 16, 2024.