Solar Storm Could See Northern Lights Shimmering in U.S. Skies This Week

A geomagnetic storm is due to hit Earth this Thursday, and it could spark some shimmering northern lights in the U.S.

On Monday, the National Oceanic and Atmospheric Administration's Space Weather Prediction Center (SWPC) issued a notice stating that a geomagnetic storm watch was in effect for March 31.

It's expected that a moderate-strength storm—classed as G2 on the G1-G5 strength scale, with G5 being the highest—could occur in the early hours of that day, or possible on the night of March 30.

"Impacts to technology from a G2 storm are generally small, but it can drive the aurora equatorward of its polar home," the SWPS said. "Aurora may be visible over the northern portions of the northern tier states if the conditions are favorable."

The storm is linked to a solar flare that occurred on the evening of March 28, and an associated coronal mass ejection (CME) that launched solar plasma towards the Earth.

Monday's solar flare was an M-class solar flare, the second-strongest type, that can cause brief radio blackouts in Earth's polar regions.

More specifically, it was an M4 strength flare on a scale of M1 to M9. The next strongest class of flares go from X1 to X9, and can be much more disruptive.

The flare was detected yesterday, Monday, causing spikes in proton and x-ray sensors. The CME, meanwhile, is travelling a lot more slowly and is not expected to reach Earth until this Thursday when it should spark the anticipated geomagnetic storm.

Flares and CMEs do sometimes occur at the same time. Describing the difference between the two, NASA notes that a flare is like a muzzle flash which can be seen anywhere in the vicinity, while a CME is like a cannonball that is propelled in a certain direction.

Both phenomena are caused by the sun's vast, twisting magnetic fields which occasionally release bursts of energy.

On Twitter, space weather enthusiasts have been following this week's developments keenly. They report that there have been not one but two CMEs launched towards Earth in quick succession.

In a series of tweets, Dr. Erika Palmerio, a solar research scientist at Predictive Science, called Monday a "wild day" for solar activity and said the two CMEs could combine as they travel towards the Earth from the sun, increasing their effect when they reach our planet.

The sun is currently about half way through the increasing phase of its roughly 11-year solar cycle—a period in which it experiences a peak in activity when the number of sunspots is highest and then a lull when the number of sunspots is lowest.

In other words, we can expect the solar activity and the number of CMEs to increase in the coming years.

Sunspots are areas that appear dark on the surface of the sun since they are cooler than other parts of the sun's surface. They are cooler because they form in areas where the sun's magnetic fields are particularly strong, strong enough to keep some of the heat within the sun from reaching the surface.

Sunspots are associated with solar flares and CMEs since these are produced when tangled magnetic field lines suddenly reorganize.

Northern lights
A stock photo shows northern lights seen over Finland. Northern lights are caused by energy from the sun, and coronal mass ejections can make them even more active. Juhku/Getty