|The dark area spanning the equator of the sun slightly to the right of|
center on this photograph is a large coronal hole, from which high
energy charged particles started streaming from the sun on November
14. Photo credit: SDO/AIA.
|On Friday, November 12, this sunspot erupted producing a solar flare|
that ejected material toward the earth. The material is expected to "deliver a
glancing blow to Earth's magnetic field sometime on Nov. 14th or 15th."
Photo credit SDO; can be obtained here.
CLICK ON THE IMAGE TO SEE A MOVIE
Sunspots are regions of strong magnetic activity which reduces convection of energy from the interior to the surface. As a result, they are cooler than other areas of the sun--a mere 3000-4500 K in contrast to the surrounding material at about 5,780 K. The magnetic field causes strong heating in the corona--the extended atmosphere of the sun. These active regions are the source of solar flares and "coronal mass ejections" (CME's), emissions of matter, magnetic fields and electromagnetic radiation. It is believed that the ejections are caused by magnetic reconnection--the rearrangement of magnetic lines of force when two oppositely directed magnteic fields are brought into proximity. The rearrangement releases energy that was stored in the original oppositely directed fields. The movie at the bottom shows a spectacular coronal mass ejection on October 1, 2001. The images in the movie were taken by SOHO's (Solar Orbiting Heliospheric Observatory) LASCO (Large Angle and Spectrometric Coronograph) instrument.
There is a Science Daily article on coronal mass ejections here and an interesting article speculating on the effects of charged particles either from a CME or from a nuclear burst on our infrastructures here. Former House speaker Newt Gingrich, a likely presidential contender, views this as an enormous threat, and it will be interesting to see if he makes it an issue if he campaigns!