On Oct. 25, 2014, the sun emitted its fifth substantial flare since Oct. 19. This flare was classified as an X1-class flare and it was a long duration event, beginning at 12:55 pm EDT, peaking at 1:08 pm and ending at 2:11 pm. Giant sunspot AR2192 is growing again, which means high solar activity is unlikely to subside this weekend. NOAA forecasters estimate an 85% chance of M-class flares and a 45% chance of X-flares during the next 24 hours. On Friday, the sun also emitted a significant solar flare, peaking at 5:41 p.m. EDT on Oct. 24, 2014. This flare is classified as an X3.1-class flare. Both X-flares produced brief but strong HF radio blackouts over the dayside of Earth. Communications were disturbed over a wide area for approximately one hour after the peak of each explosion. Such blackouts may be noticed by amateur radio operators, aviators, and mariners. The main communications impacts from this event are over the Pacific Ocean.

So far none of the eruptions from AR2192 has produced a major CME. Without a CME to rattle our planet's magnetic field, there have been no geomagnetic storms. Earth-effects have been limited to brief radio blackouts. This could change, however, in the days ahead. The giant active region is crackling with flares and a CME is overdue.

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.

The flares erupt this week from a particularly large active region -- labeled AR 12192 -- on the sun that is the largest in 24 years.

NASA's Solar Dynamics Observatory, which watches the sun constantly, captures images of those events.

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.