The first severe solar storm in 20 years could spark aurora across the US

Many states in the northern US could be in for a rare treat this Friday night. "I think we're going to see some really good aurora," one expert said.

• A stunning aurora may be visible farther south than usual this Friday, lighting up the northern US.
• That's thanks to an overactive, giant spot seven times the size of Earth that's erupting on the sun.
• Northern border states from Washington to Michigan are most likely to see the aurora Friday night.

For the first time in 20 years, NOAA has issued a G4 geomagnetic storm warning. The Northern Lights are forecast to reach farther south than usual this Friday, dazzling states across the northern US.

G4s are the second-strongest type of solar storm. They've been known to cause radio blackouts and power grid outages, but experts don't expect these approaching ejections to cause any trouble on Friday, Matt Owens, a professor of space physics at the University of Reading, and Alex Young, the associate director for science at NASA Goddard's Heliophysics Science Division, told Business Insider.

"With the eruptions from this group, I think we're going to see some really good aurora. I wouldn't expect too many really bad effects," Owens said.

Typically, the best time to see aurora is between 10:00 p.m. and 2:00 a.m. local time, because this is when it will be the most active, according to the National Oceanic Atmospheric Administration.

We mainly owe the upcoming aurora to a giant, hyperactive sunspot called AR3664 that's seven times the size of Earth and has been producing powerful eruptions, called coronal mass ejections, for the last several days.

Powerful eruptions like these can hurl high-energy solar particles toward Earth that interact with our atmosphere to create aurora borealis, a dazzling display of colorful lights.

Typically auroras are contained in the uppermost region of the northern hemisphere. But when Earth receives a more powerful blow of these high-energy particles, it can cause auroras over a larger portion of the planet.

Over the last several days, AR3664 has grown in size, becoming one of the biggest and most active sunspots for this solar cycle (which began in December 2019), Space.com reported.

And in the last 24 hours, AR3664 spit out four coronal mass ejections that are now hurtling toward Earth at roughly 560 miles per second, Owens told BI.

Where auroras are forecast in the US

Due to the relatively strong magnetic field of these oncoming coronal mass ejections, Friday's aurora is forecast to make a rare appearance, stretching all the way down to Montana, North Dakota, Minnesota, Wisconsin, and Michigan.

Even states including Maryland, New York, and Pennsylvania, could catch a glimpse of the aurora low on the horizon, Young told BI.

"That's the most extreme estimate," Young said. The reality is that we just won't know how bright, active, and wide-reaching the aurora will be until the coronal mass ejections reach Earth's atmosphere. Even experts' estimates of when they'll arrive offer only a rough ballpark.

"Our timing estimates may be way off," Owens said.

To watch the aurora on Friday, head to the NOAA's space weather website for the latest forecast to see if they'll be visible where you are.

Then, just step outside once it's totally dark and look up. If you're lucky, you may get to see this spectacular sight.

Correction — May 10, 2024: An earlier version of this story misattributed information and a quote to Andrew Gerrard of the New Jersey Institute of Tech. The most extreme estimate of aurora and where they can be seen in the US came from Alex Young.