The third massive solar flare in the span of two days has been seen erupting from the surface of the sun and has been captured in images by a NASA space observatory, the space agency says.
The flare, classified as a strength X1-class, reached its peak at 5:06 a.m. EDT June 11, NASA said, and erupted from the same region of the sun that produced two powerful flares on June 10.
That region recently rotated to face the Earth from the left limb of the sun, NASA said.
Although a short radio blackout was experienced on Earth from the flare on June 11, it apparently did not create a coronal mass ejection, the burst of solar particles called a solar wind that some flares emit as they erupt from the sun's surface, according to the U.S. Space Weather Prediction Center in Boulder, Colorado.
The center has a website that issues official forecasts and alerts for the U.S. government.
Small coronal mass ejections were produced by the June 10 flares, officials aid.
The sun's currently in the active phase and moving to a maximum in its 11-year solar cycle, although the current solar max appears quite weak when compared with others on record, say NASA officials.
In X flares, the accompanying number denotes its strength, with an X2 being twice as powerful as an X1, and so forth. The most powerful X-class flare so far this year was a giant X4.9 eruption in February; there have been eight X-class flares recorded so far this year.
Other somewhat less-powerful flares sometimes occur, including M-class ones that can produce beautiful auroras on Earth, and the weakest flares, C-class events.
A number of satellites monitor the activity of the sun for NASA, including the Solar Dynamics Observatory that observes the sun around the clock and captured dramatic visuals of the latest flare.
The space agency also operates twin STEREO spacecraft, and in cooperation with the European Space Agency it helps run the Solar and Heliospheric Observatory, or SOHO, launched in 1995 for solar studies.
More flares are likely in store, NASA said, as the sun hits its stride for such outpourings.
"It's back," said Dean Pesnell of NASA's Goddard Space Flight Center. "Solar max has arrived."
While the radiation from even powerful flares cannot pass through Earth's atmosphere and so is not a threat to humans, the flares can cause problems in layers of the atmosphere through which signals from GPS and communications satellites travel, NASA said.