California, US

Sun released another set of solar flares on Saturday (Jul 13) and the explosion was captured by NASA's Solar Dynamics Observatory from space. The X-class flare, the most powerful class of solar flare, was released from Sunspot AR3738. The solar flares resulted in shortwave radio blackouts across Australia, Southeast Asia, and Japan. Communication blackouts are a common occurrence due to the intensity of the X-rays and extreme ultraviolet radiation emitted during these events.

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However, no coronal mass ejection (CME) was noticed by scientists as a result of the solar flare. CME is when the sun releases large amounts of plasma and magnetic field. Experts checked for CMEs until several hours later but failed to find any. Coronal mass ejections are responsible for the creation of auroras on Earth. 

This one was an X-class solar flare, which is the strongest. Next comes the M-class flare which is 10 times less powerful than X-class. The list includes C-class, B-class and A-class, in that order. 

The sun has been extremely active over the past few months. At the end of April, an extremely powerful solar flare caused massive radio blackouts across the Pacific region. In May, beautiful auroras were seen across the globe, even in regions where auroras are not common. Scientists witnessed the sun become active with solar flares being released from sunspot AR3664, along with massive coronal mass ejection. 

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In June, sunspot AR3723 was seen firing off a strong solar flare and made a re-appearance in the next few days. It made a total of three appearances across the Earthside of the Sun. On June 23, it emitted an M-class solar flare. Temporary radio blackouts were reported in Africa and Western Europe. 

Why do solar flares cause radio blackouts?

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Travelling at the speed of light, radiation from solar flares electrically charges the upper atmosphere of Earth. The high-frequency shortwave radio signals then have a denser environment to pass through. When the radio waves interact with electrons in the ionized layers, increased collisions lead to loss of energy, absorbing the radio signals.