This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Sunday, November 14, 2010

Solar activity (and Newt Gingrich)

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.
After a sluggish start to the current active phase of the solar cycle, the sun is now developing some active sunspot groups.  The sun has a high-density core at a temperature of over 13 million K extending to about 0.25 of its radius.  above this, extending to about 0.7 solar radius is a so-called radiative zone where heat is transported by radiation.  This is surrounded by an outer layer heat is transported by convection of hot material to the surface. The visible surface of the sun is called the photosphere.

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!

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