Strongest Solar Flare Of The Current Cycle

Yesterday, May 14th (1651 UT), sunspot AR3664 unleashed the strongest solar flare of the current solar cycle--an X8.7-category blast from beyond the sun's western limb. X marks the spot in this image from NASA's Solar Dynamics Observatory:

Because the sunspot is behind the edge of the solar disk, the flare was partially eclipsed. It was probably even stronger than it appeared. "X8.7" is almost certainly an underestimate of the flare's true strength.

Extreme ultraviolet radiation from the flare ionized the top of Earth's atmosphere, causing a deep shortwave radio blackout over the Americas. Ham radio operators, aviators and mariners may have noticed a sudden loss of signal at all frequencies below 30 MHz.

Source: https://www.spaceweather.com/