"As magnetic fields on the sun rearrange and realign, dark spots known as sunspots can appear on its surface. Over the course of Feb. 19-20, 2013, scientists watched a giant sunspot form in under 48 hours. It has grown to over six Earth diameters across but its full extent is hard to judge since the spot lies on a sphere not a flat disk." wrote NASA Goddard science writer Karen Fox, on the NASA SDO website.
"The spot quickly evolved into what's called a delta region, in which the lighter areas around the sunspot, the penumbra, exhibit magnetic fields that point in the opposite direction of those fields in the center, dark area. This is a fairly unstable configuration that scientists know can lead to eruptions of radiation on the sun called solar flares."
According to SpaceWeather.com, there is a 45% chance of M-class solar flares over the next two days, as well as a 15% chance of X-class flares for the same time period.
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M-class solar flares are 'medium-sized' eruptions in the Sun's atmosphere. They can cause brief radio blackouts at the north and south polar regions, as charged particles from these eruption stream down into the atmosphere at the poles, and they can set off minor, short-lived geomagnetic storms (also called radiation storms). X-class flares are much more powerful. The intense burst of high-energy particles from them can fry orbiting satellites, expose astronauts in low-Earth orbit to lethal doses of radiation, and cause world-wide communications and power blackouts. They can also set off major, long-lived radiation storms in Earth's magnetosphere that can cause further damage and even expose people flying in aircraft near the poles to a small dose of radiation.
The Sun is reaching the peak of its 11-year activity cycle this year, but so far this peak is shaping up to the be the weakest of the last 100 years.
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