Massive Solar Flare Causes Radio Blackout Over U.S.

The sun continued acting out this week when it spewed out a strong solar flare, causing radio blackouts over the U.S. and Latin America.

The flare, classified as an M8.6-class flare, was released by sunspot region 3234 at around 12:50 p.m. ET on February 28, according to NOAA's Space Weather Prediction Center.

As the flare hit our planet, it interacted with our atmosphere, causing a loss of signal below 30 MHz over much of the Americas for the 30 minutes after the flare arrived. This came only days after spectacular auroras lit up the night sky across the world as a result of coronal mass ejections from the sun.

Solar flares are powerful jets of electromagnetic radiation, mostly X-rays, spat out from the sun's surface. They are usually emitted from sunspots when the twisted magnetic field lines in these regions suddenly realign, often also releasing a plume of solar plasma known as a coronal mass ejection, or CME.

"Solar flares are classified according to how bright they are in the soft X-ray part of the spectrum," Gonzalo José Carracedo Carballal, an astrophysics researcher at the Instituto Nacional de Técnica Aeroespacial in Madrid, Spain, previously told Newsweek.

The weakest are the A-class flares, with increasing intensity flares being categorized as B-class, C-class, M-class, and finally, at their most powerful, as X-class. Each class is 10 times more powerful than the last: X-class flares are 10 times more powerful than M-class, and an X10 flare is 10 times more powerful than an X1 flare.

The most recent M8.6-class flare is therefore nearly as powerful as an X-class flare.

Solar flares cause radio blackouts due to them ionizing the Earth's ionosphere. High-frequency radio waves such as those used in communications must bounce off the ionosphere to reach their destination, meaning that if the flare ionizes that layer, the waves become degraded or are completely absorbed.

"The emissions of X-rays ionize the lower ionosphere (the D-region, at altitudes close to 80-90 kms) [50-56 miles], which actually absorbs [high frequency] radio waves, thereby stopping them from continuing up to the higher ionosphere where they get bounced back towards the ground," Brett Carter, an associate professor in space physics at RMIT University in Australia, told Newsweek in December.

"This absorption effectively causes the 'radio blackout'...because the signals don't reach their intended target(s)."

Civil aviation is the main industry affected by these radio blackouts, usually long-range communications with aircraft over large remote areas or oceans where there are no ground-based radio networks.

"High-frequency is a primary method for aircraft in these areas to communicate with air traffic control. For example, flights over the North Atlantic will communicate with oceanic air traffic control centers provided by Canada, Iceland and U.K./Ireland," Mike Hapgood, a space weather scientist at the STFC Rutherford Appleton Laboratory in the U.K, previously told Newsweek.

"Many aircraft also have satcom as backup, but high-frequency is mandatory as part of international agreed procedures. So high-frequency blackouts can disrupt those links, but in general only for a few tens of minutes, so the industry can work round that disruption. These blackouts will not affect take-off and landing as aircraft will then use short-range VHF radio links."

More powerful solar flares can cause more widespread effects, but thankfully are much more rare.

The 1859 Carrington Event is thought to have been as a result of the largest and most powerful X-class flare, resulting in incredible aurora and even some fires in telegraph stations. An equivalent flare today may cause massive impacts to the electrical grid.

The sun is expected to get more and more active, producing more sunspots and releasing more solar flares and CMEs in the coming years as it approaches the solar maximum of its current solar cycle, Solar Cycle 25. Twenty-four complete solar cycles have been recorded since observations began in 1755, with Solar Cycle 25 predicted to peak in 2025.

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about solar flares? Let us know via science@newsweek.com.