Massive X8.7 Solar Flare From Super-Active Sunspot Causes Radio Blackouts Over North, South America Days After Widespread Aurora Displays

The Earth is currently in Solar Cycle 25, which began in December 2019 and is approaching the period known as solar maximum. During this time, a massive group of sunspots has produced the largest solar flare in nearly a decade.

Radio Wave Interruption

The huge solar burst, classified as an X8.7-class solar flare, is considered the most powerful since 2005. It was produced by Sunspot AR 3664, which caused the dazzling Northern Lights to be displayed over the weekend in various parts of the world.

Large solar flares like this one can cause radio blackouts because they ionize the Earth's ionosphere. As a result, radio waves are absorbed instead of reflected, obstructing long-distance radio communication.

The X8.7-class solar flare just skimmed past our planet, carrying bursts of X-rays and ultraviolet radiation from the Sun. This triggered a radio blackout and signal loss at all frequencies below 30 MHz over the American continents.

The interruption was caused by the fact that the solar flare was created from the same massive sunspot that emitted the train of coronal mass ejections on May 10. This event triggered the huge G5 geomagnetic storm, which resulted in widespread auroras seen across all 50 US states.

X-class solar flares can also cause radiation storms that affect satellite activity and expose astronauts or airlines to increased solar radiation levels. So far, the strongest X-flare ever measured by scientists was the X28-class flare observed in 2003. Still, the Carrington Event of 1859 is believed to be the strongest solar flare in history, causing fires in some telegraph stations.

The solar flare observed on May 14 was also the largest of its kind in the current solar cycle. Sunspot AR3664 has been slowly moving away from the Earth as the Sun rotates. This means that any charged particles emitted from this region are no longer directly aimed at our planet.

Effects of Radio Blackouts

Under normal conditions, high-frequency radio waves can support long-distance communication by refraction through the upper layers of the Earth's ionosphere. When an extreme solar flare occurs, ionization is produced in the lower, denser layer of the ionosphere, called the D-region. Radio waves that interact with electrons in layers lose their energy because of the more frequent collisions in the D-region's higher-density environment.

Radio blackouts are among the most common space weather events that affect our planet. On average, minor events occur, but blackouts are by far the fastest to cause direct impact on Earth. The X-rays that cause radio blackouts arrive at the speed of light, making it difficult for experts to issue advance warnings.

Radio blackouts typically last several minutes, although they can also last for hours. The adverse effects of radio blackouts are felt by industries that depend on high-frequency radio communications and low-frequency signals, like aviation and marine industries. While radio blackouts primarily affect high-frequency communication at 3-30 MHz, fading and diminished reception may also spill over to very high frequency (VHF) at 30-300 MHz.

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