Giant ‘Hole’ In Sun May Push Auroras To Northern States This Weekend

ACROSS AMERICA — A giant “hole” in the sun swept ethereal aurora borealis displays to northern U.S. states Thursday, dipping as far south as South Dakota, Iowa and Ohio, and there’s a strong chance of encore performances Friday and Saturday, according to northern lights forecasts.

The Space Weather Prediction Center issued a severe geomagnetic storm watch through Saturday. Such storms can be bad news for people relying on radio and satellite communications (no outages were reported), but the opposite for people in northern-tier states from Washington to New York who have seeing and experiencing the northern lights on their bucket lists.

Curtains of green, purple, yellow and red graced skies around the globe Thursday night and early Friday morning. In the United States, social media feeds are full of pictures of aurora dances — in Alaska, where auroras are common, but also Montana, Wyoming North Dakota, Minnesota, Wisconsin, Michigan’s Upper Peninsula, Massachusetts, Maine and other places.

Predicted Kp indexes — that’s the measure of auroral strength — are favorable for weekend activity. The best chances to see the northern lights are with Kp indexes of 5 or greater, but the arrival of the spring equinox bodes well even if the Kp index is a bit lower.

“This is a perfect timing for aurora chasers,” the Space Weather Prediction Center said, noting that because of what’s known as the Russell-McPherron effect, “even a slight gust of solar wind around the equinoxes can spark a good display of high-latitude auroras.”

Excitement about the auroras began building earlier this week when NASA’s Solar Dynamics Observatory discovered coronal hole 30 times the size of Earth, according to the Space Weather Prediction Center.

Coronal holes are not a depression per se, but a cooler area of the sun that does not glow as brightly. As it spread across the sun’s 2 million-degree corona, or atmosphere, it spewed strong solar winds that pushed the auroras far south of the Arctic Circle, where they’re much more common.

• What’s A Kp Index, More Northern Lights Hunting Tips
• Aurora Displays More Likely In Active Solar Storm Season

Because its atmosphere is so much hotter than its surface, the sun’s gravity can’t hold it in place. As a result, the sun ejects a continuous stream of plasma — charged particles of electrons and protons known as a coronal mass ejection (CME) carried by the solar wind at speeds as high as 900 kilometers per second.

When those charged particles hit Earth’s atmosphere, our magnetic fields send them to the North and South Poles, setting off the dazzling displays.

Most often, the auroras appear as tall rays that look like a colorful curtain made of folds of cloth.
“During the evening, these rays form arcs that stretch from horizon to horizon,” according to the Space Weather Prediction Center website. “Late in the evening, near midnight, the arcs often begin to twist and sway, just as if a wind were blowing on the curtains of light. At some point, the arcs may expand to fill the whole sky, moving rapidly and becoming very bright. This is the peak of what is called an auroral substorm.”

If aurora chasing isn’t a bucket list item, it might be a good time to add it. We’re midway through an 11-year cycle in which the sun's magnetic fields flip polarity — and that means the northern lights could dance more often in the next decade or so as the sun approaches “solar maximum.” Aurora experts say the busy season for sunspots should peak between 2023 and 2028.

And, if you’re out aurora hunting this weekend, check out the early evening sky for a rare planetary alignment that peeks early next week.

• 5 Planets Parade Across The Late March Sky (And Buzz Aldrin Loves It)
• 2023 Guide To Meteor Showers, Supermoons And Full Moons