'Strongest' solar flare since 2017 detected: Here's what to know

NOAA's Space Weather Prediction Center shared an image of the solar flare, which peaked on New Year's Eve.

(NEXSTAR) — A massive solar flare — the largest in years — was spotted on the sun on New Year's Eve, sparking a warning to some high-frequency radio users.

In an update Sunday evening, NOAA's Space Weather Prediction Center (SWPC) released an image of the flare, which appeared as a large, glowing spot on the sun. You can see that image below.

"A flare is an eruption of energy from the sun that generally lasts minutes to hours," the SWPC explains. This one in particular, which peaked just before 5 p.m. ET on Sunday, was categorized as an X5 flare.

Solar flares are classified based on their strength, much like earthquakes, according to NASA. The scale ranges from B-class on the lowest end to C-class, then M-class, and finally, X-class. Each letter represents a ten-fold increase in energy output, and there is a scale of 1 to 9 in each class, except for X-class. X-class flares can exceed 9, with the largest-ever recorded being an X45 that occurred in 2003.

Flares that are B- or C-class are too weak for us to notice on Earth, NASA explains, and M-class flares "can cause brief radio blackouts at the poles and minor radiation storms that might endanger astronauts." X-class flares can cause more noticeable impacts, like radiation storms that can impact satellites and give small radiation doses to airplane passengers flying near the poles. NASA notes that they can also cause "global transmission problems and world-wide blackouts."

At an X5, Sunday's flare was much smaller than the flare recorded in 2003. It was, however, the strongest since September 2017, when an X8.2 flare was detected, according to the SWPC. This flare also supersedes an X2.8 solar flare reported in the same region of the sun on December 14. At the time, the SWPC reported that flare was “likely one of the largest solar radio events ever recorded.”

The SWPC said those using high-frequency radio signals (like emergency managers) may notice a "temporary degradation or complete loss of signal on much of the sunlit side of Earth" as a result of Sunday's solar flare.

For the rest of us, the SWPC said we "need not be concerned." While a coronal mass ejection (CME) — which can cause northern light displays on Earth — was detected in connection with Sunday's solar flare, the chances of any of us seeing the aurora Monday night appear slim.

The SWPC's current forecast shows only a few states have a chance at catching the auroras Monday night. Much of Alaska and Canada have a high likelihood of seeing the northern lights while some states — Washington, Idaho, Montana, Wyoming, North Dakota, South Dakota, Minnesota, Iowa, Wisconsin, Michigan, New York, Vermont, New Hampshire, and Maine have slim chances (denoted by the light green and red "view line" on the map below).

The aurora "may become visible along the horizon," the SWPC said Monday.

A minor geomagnetic storm watch is in effect for Tuesday, though the likelihood of seeing the aurora appears even slimmer then, per the SWPC's current forecast.

Solar activity and CMEs are only expected to be more common in 2024 as the sun continues through Solar Cycle 25. Solar cycles are 11-year periods when the sun flips its magnetic poles, sparking space weather like flares and CMEs, which are explosions of plasma and magnetic material from the sun that can reach Earth in as little as 15 to 18 hours, NOAA explains. 

Those CMEs that do impact Earth not only cause auroras but can impact our navigation, communication and radio signals. 

While it may sound alarming, you shouldn’t expect a five-day blackout and grounded flights if the aurora brightens up your sky.

There are resiliencies built into our electrical grids, flights, and communication systems to prevent or diminish any impact, Dr. Delores Knipp, a research professor in the Ann and H.J. Smead Aerospace Engineering Sciences Department at the University of Colorado Boulder, told Nexstar in October. In fact, you may not even notice a solar storm has hit us (like Sunday's solar flare). SWPC’s Rob Steenburgh previously told Nexstar that they “happen all the time and are no cause for alarm.”

“Some people worry that a gigantic ‘killer solar flare’ could hurl enough energy to destroy Earth, but this is not actually possible,” NASA previously explained. Plus, solar cycles repeat every 11 years. That means anyone over the age of 11 has already lived through a solar maximum (and probably didn’t notice its occurrence).

An added bonus of the current solar cycle? The total solar eclipse on April 8, 2024, will occur near cycle maximum, meaning a good show for skywatchers, NOAA explains.