A strong solar flare of class M5.0 occurred around 1332 UT (time of maximum) on the sunspot 1745, in the west of the Sun. A CME (coronal mass ejection) was projected into space and is clearly visible in the images of spacecraft SOHO. If directed Earthward (we will know, soon), the CME will trigger aurora and geomagnetic activity.
In a brief, simple explanation (I hope), this event (which is complex, actually, in that there are several individual events that make up this single display of an active Sun), is one in which we see complex magnetic structures originating from within the Sun, snapping apart, causing a powerful expulsion of solar material and an explosion of a great magnitude of power in the form of light, radio energy, and so on. The light and radio energy reaches Earth in about eight minutes, and is mostly absorbed and blocked by the upper atmosphere, and affects the Ionosphere, such that shortwave radio radio waves are blocked. This blockage is known as a radio blackout, and it affects only the daylight side of the Earth. It does not affect VHF and higher frequencies, such as TV and cellphones. At the same time, this expulsion of solar material, solar plasma, is sometimes directed Earthward, and if so, takes about two days to make its way to the Earth. The arrival interacts with the Earth's magnetosphere and geomagnetic field. This may cause geomagnetic storms, which in turn may trigger aurora, and further degradation of shortwave radio propagation. In the worst case, the geomagnetic activity could cause power line and pipeline damage, but it takes a very large geomagnetic storm to cause that sort of damage. This event is not producing such a powerful event.
This video is from NASA, and were taken from the AIA instrument of the satellite SDO (Solar Dynamic Observatory), with a wavelength of 304 + 131 Angstroms.
Credit: SDO AIA
More info: SunSpotWatch.com