A so-called cannibal coronal mass ejection is set to hit Earth on December 1, creating geomagnetic storms across the skies at higher latitudes.

When the Sun's magnetic field lines twist and realign, the star ends up shedding gigantic clouds of charged particles from its surface.

These coronal mass ejections (CMEs) weigh billions of tons, and barrel through space at speeds ranging from 12 to 1,250 miles per second (about 20 to 2,000 kilometres per second). If multiple CMEs are expelled in succession, faster bursts can overtake and assimilate slower ones in front to create what scientists call cannibal CMEs. 

The Sun has been particularly active as of late, spewing three solar flares in one go on November 27 and a fourth a day later. That fourth burst is expected to spread and merge with two of the three slower flares to form a large cannibal CME, scheduled to hit Earth on in the early hours of December 1 (UTC).

The US National Oceanic and Atmospheric Administration's Space Weather Prediction Center upgraded the strength of the potential incoming geomagnetic storm from G2 to a possible G3 level. The geomagnetic storm scale goes from G1 - labeled as weak - to G5, which is considered extreme. G3 is characterized as "strong" and could disrupt the voltages on power systems, and impact the orientation and navigation of satellites. 

"Multiple CMEs occurred from the Sun on November 27, 2023," the Space Weather Prediction Center confirmed. "Three of these CMEs appear to have Earth-directed components with the first arrival as a potential glancing blow or near-Earth proximity passage beginning as early as late on Nov 27 EST (early Nov 30 UTC)."

"The later CMEs are anticipated to arrive at Earth near the end of Nov 30 EST (early Dec 1 UTC) as at least glancing blows. Analysis and model results suggest G1 levels are probable on the Nov 30 UTC-day in response to any initial CME influences, followed by G2 levels on the Dec 1 UTC-day as the additional CMEs arrive."

When the burst reaches Earth, showers of charged particles will hit the atmosphere. The impact will release energy in the form of light, creating auroras that could be visible to the naked eye if the sky is clear and dark enough.

Meteorologists at AccuWeather reckon viewers in the northern half of the US may get to catch a glimpse of the geomagnetic storm's fallout. Auroras are expected from Washington to New York, and may even reach as far south as Pennsylvania, Missouri, Colorado, and Northern California.

"The best viewing conditions are predicted across the Canadian Prairies and into Ontario, Minnesota, northern Wisconsin and the Upper Peninsula of Michigan," explained Brian Lada, a meteorologist at AccuWeather. 

Meanwhile, folks across the pond in the UK might not get to see the Northern Lights. The bulk of the geomagnetic storm will hit during the day when it's too bright to see, according to the Met Office.

But there is a small chance it might be visible in northern Scotland during the evening. If the event is strong and lingers for long enough, however, it may be possible to view for those in northern England and Northern Ireland.

For readers in the Southern hemisphere, the Australian Bureau of Meteorology's Space Weather Forecasting Centre predicts that the Southern Lights could be visible as far north as Victoria and other southern parts of the country. ®

https://www.theregister.com//2023/12/01/cannibal_coronal_mass_ejection/