
Cannibal solar storm may spark bright auroras tonight
Eyes to the sky Wednesday and Thursday nights for a chance to see the Aurora Borealis!
A 'cannibal CME' is headed straight towards Earth, and space weather forecasters expect bright displays of the Northern Lights during the nights ahead.
This story has been updated to reflect the latest space weather forecasts.
It's been an active week for the Sun so far. After a few relatively minor solar flares on Monday, November 27, satellites detected three eruptions from the Sun's surface — coronal mass ejections, aka CMEs or solar storms — headed in Earth's general direction.

This view of the Sun in extreme ultraviolet highlights immense coronal loops surrounding active regions on the surface. The image was captured by NASA's Solar Dynamics Observatory on November 28, 2023. Credit: NASA
The first was expected late on Wednesday, November 29, when it would possibly scoring a glancing blow on Earth's magnetic field. As a result, forecasters with NOAA's Space Weather Prediction Center issued a G1 (minor) geomagnetic storm watch for the overnight hours of Wednesday night into Thursday morning.
A geomagnetic storm is a disturbance in Earth's magnetic field caused by changes in the stream of the solar wind or the passage of a solar storm. During these disturbances, billions of high-energy solar particles are funnelled down into the atmosphere near the poles, where they collide with molecules of the atmosphere. The energy they pass on during these collisions is then released by the air molecules as flashes of light, and the resulting displays are what we call the Aurora Borealis or Northern Lights.

As of Thursday morning, it appears as though the forecast G1 geomagnetic storm did not occur Wednesday night. It's possible that the glancing blow from the first CME was lighter than expected, or the trailing edge predicted to affect us hasn't yet reached Earth.
However, NOAA SWPC is now forecasting a G3 (strong) geomagnetic storm for overnight Thursday into Friday. The reason? On November 28, at around 2:24 p.m. EST, NASA's Solar Dynamics Observatory caught the Sun blasting out a powerful 'almost X-class' solar flare.

This composite of NASA SDO images of extreme ultraviolet light coming from the Sun shows the M9.8-class solar flare that blasted out a sunspot complex known as Active Region 3500, on November 28, 2023. Credit: NASA's Solar Dynamics Observatory
In the aftermath of the intense release of energy from this flare, another satellite — the Solar and Heliospheric Observatory — spotted an immense 'full halo CME' expanding away from the Sun.
READ MORE: Solar max is approaching. Here's where and how to see the Northern Lights
This cloud of solar plasma erupted from the region of the solar flare. As shown in the imagery below, this CME appears to be expanding to form a bright ring around the disk that blocks direct sunlight from entering the instrument. This ring shape gives a 'full halo CME' its name. Combined with the origin point of the CME, the shape of it tells scientists that it is headed more or less directly towards Earth.

The halo CME imaged by the Solar and Heliospheric Observatory as it expands away from the Sun on November 28 and 29, 2023. Credit: NASA/NOAA SOHO
Accelerated away from the Sun by the intense energy from the M9.8-class solar flare, this solar storm is travelling at a much faster rate than the CMEs that erupted on Monday.
According to NOAA SWPC, it will catch up to the second and third incoming solar storms before they reach Earth, sweeping up both of them in the process. The resulting 'cannibal CME' will then cross Earth's orbit Thursday night, scoring a direct hit on Earth's geomagnetic field.

These three panels from the WSA-ENLIL solar wind model have been combined and labelled here to show the progress of the CMEs that erupted from November 27-28. The first - the weakest - passes near Earth on November 29. The second and third appear to have merged together (likely due to how close they erupted), but the fourth is moving so much faster than the others that it will catch up, absorbing CMEs 2&3 to form a larger cannibal CME that will pass Earth at around 00 UTC on December 1 (evening November 30). Credit: NOAA SWPC/Scott Sutherland
The sudden uptick in the number of high-energy solar particles flowing past Earth is expected to spark an intense magnetic disturbance, producing the forecast G3 geomagnetic storm.
However, according to the timing of NOAA SWPC's forecast, aurora viewing will likely be at G2 levels starting an hour or two before midnight for Atlantic Canada, Quebec, eastern Ontario, and southwestern Ontario. The view line is expected to push farther south (to G3 levels) about an hour after midnight in those regions, but when the auroral arc is more centred on the country. That may provide better viewing for southwestern Ontario in the early hours of Friday, but this is more likely for northern Ontario and through the Prairies. Apparently, geomagnetic storm levels will drop back down to G1 (minor) after about three to four hours, so southern B.C. may miss out on the show.

This experimental aurora viewing model attempts to predict the southern extent of the auroras on the nights of Nov 30-Dec 1 (left) and Dec 1 (right). The coloured arc represents the likelihood of seeing auroras from low (green) to high (red). To the south of the arc is the 'view line' — the farthest southern extent where auroras might be seen just along the northern horizon. Credit: NOAA SWPC
Even with satellites spotting flares and CMEs, and sophisticated computer models tracking solar storms through the inner solar system, space weather can still be tricky to forecast.
A lot depends on some very specific conditions. Is Earth's geomagnetic field calm or already agitated by the solar wind or a previous CME encounter? Is the CME's magnetic field aligned with Earth's magnetic field or opposed to it? Is the CME diffuse or densely packed with solar particles? How much energy did the plasma cloud absorb from the solar flare that caused it? Any combination of these factors can produce very different results.
For Thursday night into Friday, Earth's geomagnetic field will have been slightly agitated by the CME from Wednesday. Also, the cannibal CME will have a higher density after consuming not one but two other CMEs before it arrives here. Plus, it will have absorbed a fair amount of energy from the solar flare that launched it into space in the first place. All of that should combine to give us a good chance of strong aurora displays that night. The only uncertainty comes from the storm's magnetic field, and we'll know more about that when it passes by the ACE and DSCOVR satellites, perhaps an hour or two before the cloud reaches Earth.
Stay tuned for updates!
(Thumbnail image courtesy Tree and Dar Tanner of Team Tanner, a pair of storm and aurora chasers located in central Alberta)