AccuWeather: Northern lights may glow over parts of US this week

After years of slumber, a solar flare burst from the sun toward Earth is tempting a rare glimpse at the northern lights for areas farther south than normal and becoming the latest sign that the sun is "waking up."

The solar flare erupted from the sun on Monday and produced a coronal mass ejection (CME) of plasma from the sun's atmosphere, which will interact with the Earth's atmosphere through Thursday. As a result, NOAA's Space Weather Prediction Center is forecasting a multi-day solar storm that is expected to peak Wednesday night into Thursday morning at G-3 intensity (strong) on a scale ranging from G-1 (minor) to G-5 (intense).

A solar storm, also known as a geomagnetic storm, is when the solar particles interact with Earth's upper atmosphere and produce auroras, AccuWeather Senior Meteorologist and Astronomy Blogger David Samuhel explained. The strength of these storms plays into which areas may catch a view of the stunning lights.

When these waves of charged particles reach the Earth, the planet's magnetic field funnels them toward the North and South poles where they collide with the planet's atmosphere. It is the interaction between the charged particles and the Earth's atmosphere that results in colorful swirls of light known as aurora. In the Northern Hemisphere, the lights are known as aurora borealis, and they can glow in a variety of colors, including vivid greens and purples.

The breathtaking phenomenon is a regular occurrence close to the North and South poles, but it can occasionally be seen in more populated areas in Europe and the United States during strong geomagnetic storms.

"It's all about the strength of the solar storm. The stronger the storm, the farther south the auroras are seen," Samuhel said.

At the intensity of a G-3 storm, there's the possibility that the northern lights could reach places in the U.S. from Boston to Chicago to Seattle, although seeing the aurora from in the cities themselves will not be possible due to light pollution.

"If the storm gets this strong, it is possible to see the northern lights as far south as northern Pennsylvania, Iowa and Washington, but it will look more like a faint glow on the horizon, not swirling bands of light overhead like what people think of when they think about the aurora," AccuWeather Meteorologist Brian Lada said.

However, cloud cover and light pollution may prevent some of these areas from seeing them.

"I'd say light pollution affects (visibility of the northern lights) much more than meteor showers," Samuhel said. "It is usually so dim when it's visible this far south that you have to be in a pitch-black area to see it, even then it could still be too dim."

He added that people viewing the dimmer lights are sometimes able to get better pictures by using long exposures so the lights show up.

Minnesota and Wisconsin look to be among some of the places with the least amount of cloud coverage, according to Samuhel, though northern New England and the Northwest will have poor conditions for viewing the aurora.

However, Samuhel warns that the storm may not play through.

"The prediction of these solar storms is very tough, harder than forecasting the weather," Samuhel said. "Many times events that are hyped like this one don't pan out."

The strength of these solar storms that allow for the auroras to reach farther south depends on the intensity of the flares and CMEs. The stronger the event, the stronger the storm. In turn, the stronger the storm, the farther the reach of the northern lights -- and the more serious the potential impacts.

These stronger flares typically occur during a "solar maximum," or the part of the 11-year solar cycle that consists of a period of high solar activity in the form of more numerous sunspots and a correlating higher number of CMEs. The solar minimum refers to the period of time within this 11-year cycle with low solar activity. The sun is currently transitioning from a solar minimum to the next solar maximum, which is forecast to reach its climax in the first half of the 2020s.

Auroras are more likely to occur during the solar maximum, but they can still happen during a solar minimum, according to Samuhel. However, an aurora showing up unusually far south would require a strong flare, which there's not much of a chance for except during a solar maximum.

While solar storms are ranked on a scale of G-1 through G-5, solar flares are ranked on a five-tier scale with A-class flares as the smallest, followed by B, C, M and X-class flares. Nearly every tier then has a scale from 1 to 9 following the letter, though X-class flares have no upper limit.

Monday saw a C7.4-class solar flare -- one of the strongest recent flares aimed at Earth, heralding a transition period into a more active part of Solar Cycle 25 that could affect the planet.

"This one could be a sign that the sun is 'waking up,'" Samhuel said. "The current solar minimum is about to come to an end."

The last solar maximum stemmed from 2011 into 2015 before the sun nearly went dormant.

But on Nov. 29, 2020, an M-class solar flare produced a large CME, though directed away from the Earth.

The direction of the solar flares play a key role in their impacts alongside their strength, even during the transitional periods. While the M4.4 passed by harmlessly, the combination of a strong flare in the direction of the Earth could result in a technological catastrophe.

The flare's G-3 solar storm carries with it the potential for low impacts on power systems, spacecraft operations and satellite navigation, according to NOAA. But with stronger storms come the potential for more serious impacts.

On Sept. 10, 2017, during the solar maximum's last gasp, the sun spawned an X8.3 solar flare -- one of the strongest flares ever measured, according to Samuhel. It was aimed away from the planet.

"It would have led to planet-wide blackouts and a lot of satellites would have been fried. It probably would have been a global disaster," Samuhel said.