Solar flares weren't strong enough, happened at wrong time to cause AT&T outage | Fact check

Joedy McCreary, USA TODAY
·4 min read
2

The claim: Solar flares caused AT&T cellphone outage

A Feb. 22 Facebook post (direct link, archive link) claims the sun is to blame for a widespread cellphone outage.

"AT&T Cell Phone Towers Have Allegedly Been Down Do To Powerful Solar Flares Being Emmited from The Sun (sic),” reads part of the post.

It was shared more than 500 times in four days.

More from the Fact-Check Team: How we pick and research claims | Email newsletter | Facebook page

Our rating: False

A technical error caused the outage, an AT&T spokesperson said. Solar flares that occurred shortly before the outage were not strong enough to affect the specific band of electromagnetic waves that cellphones use, an expert said, adding that flares only affect the part of the Earth that faces the sun. In North America, the flares peaked during evening and overnight hours.

Cause of outage ‘certainly wasn’t the sun’

A widespread outage Feb. 22 left thousands of AT&T customers without cellphone service for several hours. It came hours after the planet was struck by the second of two bursts of electromagnetic radiation from the sun – phenomena known as solar flares, according to the National Oceanic and Atmospheric Administration.

But the claim in the post is false. The flares did not cause the outage, according to both the company and a solar physicist. AT&T's review found the cause to be a technical error, company spokesperson Jim Kimberly told USA TODAY in an email.

Fact check: No, episode of 'The Simpsons' did not predict solar superstorm in 2024

The cause “certainly wasn’t the sun,” Ryan French, a solar physicist from the National Science Foundation’s National Solar Observatory who has written a book about the sun, told USA TODAY in an email.

Solar flares are intense bursts of high-energy radiation emitted from the sun at the speed of light and take about eight minutes to reach the Earth. NASA classifies them by their strength, with B-class being the weakest and X-class the strongest. The Feb. 21 and 22 flares were in the X-1 class, according to NOAA.

Solar flares of that magnitude affect devices that use high-frequency (HF) wavelengths – for example, amateur radio and navigation systems, French said.

Those systems depend on the bouncing of waves off the ionosphere and back down to the Earth's surface, according to Space Weather Live, a website that tracks solar activity. Flares disrupt those waves by stripping them of their energy, and that can lead to radio blackouts that typically last for an hour or two, French said.

But cellphones do not use the ionosphere. They operate in the UHF band of the electromagnetic spectrum, and those waves have frequencies hundreds of times higher than those affected by the February flares.

In theory, a flare would have to be much stronger – at least 20 times the strength of the X-1 flares in question – to disrupt the frequencies of the waves used by cellphones, French said.

Another important factor is timing – specifically, the time of day when those flares occurred. Solar flares only affect the side of the planet facing the sun – in other words, where it is daytime, French said.

The U.S. faced away from the sun at the times of both flares, French said. The second peaked at 1:32 a.m. EST on Feb. 22, about two hours before the outage began. The radio blackout it caused only affected areas near southern Asia, western Australia and the Indian Ocean, according to a map French posted to X, formerly Twitter.

USA TODAY reached out to the social media user who shared the post but did not immediately receive a response.

Our fact-check sources:

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or e-newspaper here.

USA TODAY is a verified signatory of the International Fact-Checking Network, which requires a demonstrated commitment to nonpartisanship, fairness and transparency. Our fact-check work is supported in part by a grant from Meta.

This article originally appeared on USA TODAY: No, AT&T cellphone outage not caused by solar flares | Fact check