Understanding solar flares: How explosions on Sun’s surface can lead to radio blackouts

The Sun emitted an X-class solar flare on July 2, 2023, disrupting radio communications over parts of the United States and the Pacific Ocean, according to media reports.

A solar flare is a tremendous explosion on the Sun that happens when energy stored in ‘twisted’ magnetic fields (usually above sunspots) is suddenly released, according to the European Space Agency.

The flare, classified as an X1.0 flare, peaked at 7:14 pm ET, confirmed US National Aeronautics and Space Administration (NASA) in a press note released on July 3.

Also read: Does space weather cause flight delays? New study spots links

X-class denotes the most intense flares, while the number provides more information about its strength.

On June 27, a sunspot — a huge dark patch — known as AR3354 appeared on the solar surface. Within 48 hours, it had expanded to a size roughly equivalent to 3.5 billion square kilometres, or 10 times the size of Earth.

The sudden appearance of the massive sunspot frightened space weather experts, who feared it might unleash a flurry of potentially dangerous solar storms, reported website Spaceweather.com.

The sunspot reached its maximum size on June 29, generated a significant M-class flare, and then was calm until July 2, when it unleashed an X-class flare that was directly targeted at Earth, the report added.

There are five different classes of solar flares: A, B, C, M, and X; each class is at least ten times more potent than the one before it.

What are solar flares?

Solar flares are large energy explosions that can affect radio communications, power grids and navigation signals and endanger astronauts and spacecraft.

They can heat a substance to several millions of degrees in a matter of minutes, producing a burst of radiation that spans the electromagnetic spectrum, from radio waves to x-rays and gamma rays.

Solar flares can be divided into various categories based on their brightness in X-ray wavelengths. X-class flares are large, significant events that have the power to cause global radio blackouts and persistent radiation storms in the upper atmosphere.

Medium-sized M-class flares typically result in brief radio blackouts that affect the Earth’s polar regions. Sometimes an M-class flare is followed by small radiation storms. C-class flares are slight and have little effect on the Earth.

Also read: Recent strong solar flare can hamper satellite communication

Initially, researchers thought the flare might have triggered a coronal mass ejection (CME) — a fast-moving cloud of magnetised plasma.

A geomagnetic storm, or substantial disturbance of Earth's magnetic field, would probably result from a CME from a flare of this size striking the planet.

If a huge geomagnetic storm like the one in 2003 occurred today, it would result in prolonged outages of the electrical power grid, resulting in widespread electrical disruptions, blackouts and devastation. The most powerful flare on record was in 2003, during the last solar maximum. It was so powerful that it overloaded the sensors measuring it. 

A3354’s size has not yet decreased and it may still be able to produce more M- and X-class flares in the next days, which could cause CMEs to travel towards Earth.

Solar flares cause energy particles to be released into space and directly impact the ionosphere and radio communications at the Earth. Therefore, to understand and predict space weather and the effect of solar activity on the Earth, an understanding of both CMEs and flares is required.

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