Sunspots are most common near the height of the 11-year solar cycle. The current cycle, number 25, is expected to reach its peak this year. The more sunspots, the more opportunities for solar flares.
Solar flares and accompanying coronal mass ejections, or CMEs, can influence “space weather” across the solar system, and even here on Earth. CMEs are slower shock waves of magnetic energy from the sun. Flares can reach Earth in minutes, but CMEs usually take at least a day.
All three of the X-class solar flares disrupted shortwave radio communications on Earth. But the first two flares did not release a CME; the verdict is still out regarding whether the third flare did.
Three flares, three radio blackouts
High-frequency radio waves propagate by bouncing off electrons in Earth’s ionosphere. That’s a layer of Earth’s atmosphere between 50 and 600 miles above the ground
When a solar flare occurs, that radiation travels toward Earth at the speed of light. It can ionize additional particles in the lower ionosphere. Radio waves sent from devices below it then impact that extra-ionized layer and lose energy, and aren’t able to be bent by ions at the top of the ionosphere. That means signals can’t travel very far, and radio blackouts are possible.
Three back-to-back radio blackouts occurred in response to the trio of flares, but primarily over the Pacific and Indian oceans. They were rated “R3” or greater on a 1 through 5 scale.
According to the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center, that results in a “wide area blackout of [high frequency] radio communication, [and] loss of radio contact for about an hour on sunlit side of Earth.” Low-frequency navigation signals, like those used on aircraft traveling overseas, can be degraded too.
Disruptions to AT&T cell service?
There was rampant speculation that Thursday morning’s pervasive AT&T blackout was tied to Wednesday’s solar flares. The Space Weather Prediction Center, however, released a statement noting that “it is unlikely that these flares contributed to the widely reported cellular network outage.”
Joe Kunches, former chief of operations at the center, told The Washington Post that “there is no chance” of any connection.
“First it occurred in the night hours for North America, so any possible impact would have not occurred here. Flares and their associated radio bursts only impact dayside systems if at all,” Kunches said in an email. “And, even if this was to occur during your daylight hours, chances are near nil that cell service would be affected.”
Solar flares don’t usually affect cellphone frequencies. Radio blackouts associated with solar flares affect transmissions in the high-frequency 3 to 30 megahertz band. Most cellphone carriers operate between 698 and 806 megahertz.
Finally, Wednesday’s flares didn’t unleash CMEs. Such blasts can induce electric currents that can overwhelm circuitry in satellites and even knock them offline or destroy them. In February of 2022, 40 SpaceX satellites were knocked out by a CME. Even had there been a CME, it probably would have taken more than a day to reach Earth.
Because the first two flares on Wednesday didn’t release CMEs, it means skywatchers won’t be treated to displays of the northern lights, as is often the case when such geomagnetic storms reach Earth.
The third solar flare, which was the biggest and occurred Thursday evening Eastern time, may have launched a CME, but forecasters don’t know yet. They’re awaiting coronagraph data. Since CMEs are slower-moving than solar flares it generally takes several hours for them to fully radiate away from the solar disk and become visible on sensors.
Still, there are more opportunities for X-class flares and CMEs in the days ahead. The parent sunspot cluster that launched all three, dubbed “Active Region 3590,” is still crackling.
The sunspot is so big that you can view it with your own eyes — but you’ll need eclipse glasses to do so safely.
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