Sunspots have reached a 23-year peak, so when might Philly see the northern lights?

The numbers of sunspots, those sometimes planet-size solar storms that can ignite dramatic displays of the northern lights, have reached their highest levels in more than 20 years, space scientists say.

And the peak storm activity could continue into early 2025, which would give the Philly region at least a shot at seeing the aurora as the nights lengthen, although the people who do this for a living advise that aurora prediction is even more elusive.

On Aug. 24, 225 sunspots were observed on the surface of the sun, according to the Royal Observatory of Belgium, ranking in the 95th percentile of daily sunspot activity on all days dating to Jan. 1, 1881, and the most since Oct. 1, 2001.

The storm activity roughly obeys 11-year cycles of troughs and crests, and the sun appears to be at or near the peak of the latest one.

“We won’t know the exact peak until we’ve moved well past it,” said Bryan Brasher, project manager at NOAA’s Space Weather Prediction Center, in Boulder, Colo. “Even after the peak, though, high solar activity can continue for several years. It’s also possible that the cycle could have a double peak, where solar activity dips and then rises again before the final decline.”

But while sunspots can result in spectacular visuals in our atmosphere, high-magnitude storms can result in serious disruptions to telecommunication and power systems.

» READ MORE: A look at some of the northern lights in May around the world

Chinese astronomers are reported to have observed spots on the sun more than 3,000 years ago, but it was not until the 17th century and the invention of the telescope that they were observed systematically.

It was an English astronomer, Richard Carrington, who first connected sunspots to communications disruptions and the northern lights in 1859, according to a NOAA history.

Scientists now know that the spots actually are intense magnetic storms that appear dark because they are cooler than the rest of the sun’s surface.

» READ MORE: We haven't been getting auroras, but that was some rainbow show two weeks ago

The more-powerful storms on the sun can result in coronal mass ejections that launch billions of charged particles toward Earth’s magnetic fields.

As the charged particles enter the atmosphere, they can generate spectacular, colorful visual displays in the night sky.

That’s what happened in May, leading to what NASA described as “the strongest solar storm to reach earth in two decades — and possibly one of the strongest displays of auroras on record in the past 500 years.”

On the geomagnetic 1-to-5 scale, the May event was classified as a G5, and Brasher said it has changed his relationship with solar storms.

Brasher, who has been at the space weather center for two years, said the storms pose serious threats to satellites, navigation, communications, and the power grid. A G5 in March 1989 knocked out a Canadian transformer and left six million people in the dark for nine hours.

Given the disruptive potential, tracking the prospects of the northern lights hasn’t been one of the center’s priorities.

“I knew they were beautiful and such, but considering we really don’t have a mission set to forecast and track aurora, it wasn’t a huge focus for me when I first got here,” he said.

But after the May aurora show, visible in Colorado and a near-miss around Philadelphia, “I was hooked,” he said.

He says that the northern lights have more than aesthetic value.

“Auroras are often our first, captivating glimpse into the dynamic relationship between the sun and Earth. They’re a great introduction to get people interested in space weather: they also remind us that the sun’s activity can have real-world impacts on our infrastructure.”

» READ MORE: We've been teased, but it's been awhile since we've seen the aurora in the Philly region

“You’ll certainly have a few more chances this solar cycle,” said Brasher.

To keep watch on the prospects, he recommends signing up for alerts from the center.

Also, the center posts three-day outlooks solar storms and corresponding “Kp Index” — an indicator of storm intensity and a handy number for tracking aurora potential, along with a chart for monitoring the behavior of the index in three-hour intervals.

Said NOAA space scientist Rob Steenburgh: “We still have a shot, or shots, before we say goodbye” to this cycle.