The sun played on this week as it chocked out a powerful solar flare that caused radio blackouts over the US and Latin America.
The eruption, classified as a class M8.6 eruption, was triggered by sunspot region 3234 around 12:50 p.m. ET on February 28, according to NOAA’s Space Weather Prediction Center.
When the flare struck our planet, it interacted with our atmosphere and caused signal loss below 30 MHz over much of the Americas for the 30 minutes after the flare’s arrival. This came just days after spectacular auroras lit up night skies around the world in the wake of coronal mass ejections from the sun.
Solar flares are powerful bursts of electromagnetic radiation, mostly X-rays, spewed from the sun’s surface. They are usually emitted from sunspots when the twisted magnetic field lines in those regions suddenly realign, often also releasing a plume of solar plasma known as coronal mass ejection, or CME.
“Solar flares are classified according to how bright they are in the soft X-ray region of the spectrum,” Gonzalo José Carracedo Carballal, an astrophysics researcher at the Instituto Nacional de Técnica Aeroespacial in Madrid, Spain, previously said news week.
The weakest are the A-class flares, with flares categorized as B-class, C-class, M-class and finally, in their most powerful form, X-class as their intensity increases. 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 latest M8.6-class flare is therefore almost as powerful as an X-class flare.
Solar flares cause radio blackouts because they ionize 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 when the flare ionizes this layer the waves are dissipated or completely absorbed.
“Emissions from X-rays ionize the lower ionosphere (the D region, at altitudes near 80-90 km) [50-56 miles]which actually absorbs [high frequency] radio waves, preventing them from traveling to the higher ionosphere where they bounce back toward the ground,” said Brett Carter, associate professor of space physics at RMIT University in Australia news week In December.
“This absorption effectively causes the ‘radio blackout’…because the signals do not reach their intended destination(s).”
Civil aviation is the main industry affected by these radio outages, usually long-distance communications involving aircraft over large remote areas or oceans where ground-based radio networks do not exist.
“Radio 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 the UK/Ireland,” Mike Hapgood, a space weather scientist at the UK’s STFC Rutherford Appleton Laboratory, said earlier news week.
“Many aircraft also have satcom as a backup, but radio frequency is mandatory under internationally agreed procedures. So radio frequency outages can disrupt those links, but generally only for a few tens of minutes, so the industry can work around these power outages that don’t affect takeoff and landing because the planes are then using short-range VHF radio links.
More powerful solar flares can have more far-reaching effects, but thankfully are much rarer.
The Carrington Event of 1859 is believed to have been the result of the largest and most powerful X-class flare, leading to an incredible aurora and even some telegraph station fires. Such a flare can have massive effects on the power grid today.
The Sun is expected to become increasingly active over the coming years, producing more sunspots and releasing more solar flares and CME as it nears 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 expected to peak in 2025.
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