The above image shows an active region, source of at least half a dozen solar flares and numerous other small bursts of plasma over about 36 hours (Apr. 29 - May 1, 2012). The bright active region, viewed in extreme ultraviolet light by Solar Dynamics Observatory. Image Credit: , must have had a tangled magnetic field for it to erupt so frequently. None of the flares were major, but they made for a nifty movie. Image Credit: NASA/SDO/Goddard Spaceflight Center
Meanwhile, back on the sun...
It seems the huge sunspot AR1476, which has already produced M-class solar flares, appears to be on the verge of producing something even stronger. The sunspot's 'beta-gamma-delta' magnetic field has sufficient energy for X-class flares, which are the most powerful kind.
To review, a solar flare is an explosion on the sun that occurs when the energy stored in twisted magnetic fields (usually above sunspots) is suddenly released. Flares produce a burst of radiation across the electromagnetic spectrum, from radio waves to X-rays and gamma-rays.
Solar flares are classified, from lowest to highest, as A, B, C, M and X according to the peak flux (in watts per square meter, W/m^2) of 100 to 800 picometer X-rays near Earth, as measured on the GOES spacecraft. The five categories break down as follows.
A-class: Peak flux of less than 10^-7 Watts/square meter. A-class flares produce no noticeable consequences on Earth.
B-class: Peak flux ranges from 10^-7 to 10^-6 Watts/square meter. B-class flares produce no noticeable consequences on Earth.
C-class: Peak flux ranges from 10^-6 to 10^-5 Watts/square meter. C-class flares produce few noticeable consequences
M-class: Peak flux ranges from 10^-5 to 10^-4 Watts/square meter. M-class flares can cause brief radio blackouts that affect Earth's polar regions. Minor radiation storms sometimes follow an M-class flare.
X-class: Peak flux is greater than 10^-4 Watts/square meter. X-class flare are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms.
Within each category are nine subdivisions of strength. For example, C1 to C9, M1 to M9, and so on. On July 14, 2000, the sun produced a X6 flare which triggered a major radiation storm around Earth and was nicknamed the Bastille Day event.
REMEMBER: Never look directly at the sun without proper filtering equipment.
To learn more about the sun and to stay current on solar activity, visit the mission home page of Solar Dynamics Observatory (SDO), sdo.gsfc.nasa.gov
...and the mission home page of the Solar and Heliospheric Observatory (SOHO), sohowww.nascom.nasa.gov