The Sun flares up

Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.

Two of the significant solar flares happened on September 6, 2017. NASA’s Solar Dynamics Observatory, which watches the sun constantly, captured images of both events (shown above).

The first flare is classified as an X2.2 flare and the second is an X9.3 flare. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc.

Both flares erupted from an active region labeled AR 2673, which also produced a mid-level solar flare on September 4, 2017 and another two on September 7. 

The X9.3 flare was the largest flare so far in the current solar cycle, the approximately 11-year-cycle during which the sun’s activity waxes and wanes. The current solar cycle began in December 2008, and is now decreasing in intensity and heading toward solar minimum. This is a phase when such eruptions on the sun are increasingly rare, but history has shown that they can nonetheless be intense.