Saturday, April 24, 2010

Mellow Yellow

Today dawned bright and clear at the Lost Pleiad Observatory and on a weekend that means one thing...Solar observing!  The last three days were unusually cool here in the Sonoran desert and in fact the past few days have featured on and off rain.  Some years we are already betting on when the "ice will break on the Santa Cruz river"...a local joke referring to our first 100 degree day.  Believe it or not, we have not yet broken 90 degrees this year.

I made the following sketch using my Lunt Solar Systems 60mm hydrogen alpha scope and a 16mm eyepiece (31x).  I completed the sketch at 1605 UT (9:05 MST) which is the same time that Thomas Ashcraft in New Mexico took the photo next to my sketch.   Note that my sketch has west on the left and is reversed from Thomas' photo which has west on the right.  Both images have north to the top.

The area of activity near the central meridian has not yet been officially assigned an active region number by the NOAA, but it is obviously quite large and of moderate strength.  It contains a dark "eyelash" shaped filament and the beginning of a sunspot (visible but weak in white light).  In addition, it appears that an area of activity may be coming around the souheast limb, as evidenced by the plage and filament visible in both my sketch and Thomas' photo.

For folks new to solar observing, plage, the French word for beach, are bright areas associated with concentrations of magnetic fields and form a part of the network of bright emissions that characterize the chromosphere, which is the layer of the sun visible with a Hydrogen Alpha filter.  Plage are often found surrounding sunspots.  Filaments are observed as dark, thread-like features. These are dense, somewhat cooler, clouds of material that are suspended above the solar surface by loops of magnetic field.  When they are on the solar limb, they are referred to as prominences.  Follow this link to watch a 4 MB movie of the "granddaddy" eruptive prominence from 1945, which is the largest ever recorded!

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