The sun emitted another significant solar flare, peaking at 5:54 p.m. on Oct. 29th, 2013  – the fourth X-class flare in the last week.

Solar flares are powerful bursts of radiation and while the radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, when intense enough they can disturb the atmosphere in the layer where GPS and communications signals travel. The disruption to radio signals occurs for as long as the flare is ongoing, anywhere from minutes to hours.

This flare is classified as an X2.3 class 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.

Increased numbers of flares are quite common now, because the sun's normal 11-year activity cycle is ramping up toward solar maximum conditions. 

The sun emitted a significant solar flare -- its fourth X-class flare since Oct. 23, 2013 -- peaking at 5:54 p.m. on Oct. 29, 2013. NASA's Solar Dynamics Observatory captured the flare in this image, which shows light in wavelengths of both 304 and193 Angstroms. Credit: NASA/SDO

Humans have tracked this solar cycle continuously since it was discovered in 1843, and it is normal for there to be many flares a day during the sun's peak activity.

To see how this event may impact Earth, please visit NOAA's Space Weather Prediction Center at, the U.S. government's official source for space weather forecasts, alerts, watches and warnings.