For the first time in 19 years, a “severe” solar storm warning has been issued for several plumes of solar material about to slam into the Earth.
These five coronal mass ejections (CMEs) were spat out by a huge and extremely hyperactive sunspot called AR3664 and are due to crash into our atmosphere between May 10 and May 11. The last time NOAA announced a Severe (G4) Geomagnetic Storm Watch was in January 2005.
Powerful geomagnetic storms can have various impacts on Earth, including voltage control issues with the grid, satellite problems, radio blackouts, and scrambled GPS navigation.
They can also result in the aurora borealis being seen further from the poles than usual, with G4 storms, in particular, sparking the northern lights as far south as Alabama and northern California.
CMEs are large clouds of solar plasma ejected from our star, often accompanied by a solar flare of X-rays. If these CMEs hit the Earth, they can trigger geomagnetic storms in our magnetosphere.
Solar storm and power outages
Geomagnetic storms are classed on a scale of G1 (minor) to G5 (extreme), with G4 storms being considered “severe.” There are around 100 G4 storms per 11-year solar cycle, however, only three have been observed since the beginning of the current solar cycle in December 2019. The most recent was seen on March 23.
The first three of the five CMEs heading our way may combine into a “cannibal CME,” which occurs when faster-moving CMEs overtake and coalesce with other slower-moving ones. This cannibal CME is forecast to spark G3 storms, while the additional effects of the proceeding fourth and fifth CME are expected to increase the geomagnetic storm level to G4.
The last time our planet saw a G5 storm was in October 2003, which led to power outages in Sweden and transformers being damaged in South Africa.
The sunspot that flung out these five CMEs is now 15 times the size of Earth, similar in size to the sunspot that released the CME that caused the famous Carrington Event in 1859.
The Carrington Event is considered the most powerful geomagnetic storm in recorded history. It triggered auroras visible in Cuba and Hawaii and even set fires in telegraph offices.
The CMEs due to hit this weekend are nowhere near as powerful as the Carrington CMEs, and therefore we are unlikely to be exposed to such an event. It’s very improbable that we will see this kind of event again any time soon, though if it were to occur, it would be during a solar maximum—which we are now approaching.