Sunday, May 16, 2010

Polar Crown Filament

While the level of activity on the sun has calmed over recent days, there is an interesting feature that has developed called a Polar Crown.  Information on this phenomenon is surprisingly lacking on the web, although NASA has a somewhat dated webpage that provides some interesting information: "It turns out that polar crown prominences pop up almost every day. They occupy a ring (or "crown") around the sun's poles bracketed approximately by solar latitudes 60 and 70. Geometrically, the crowns resemble the auroral ovals of Earth. Instead of Northern Lights, however, the sun's ovals are filled with dancing sheets of plasma."  The image to the right is of a Polar Crown prominence in the Sun's southern hemisphere and more information is available on this webpage.

I made a sketch of the sun today at 1645 UT (9:45 MST) that shows a Polar Crown filament in the northern hemisphere.  This is the first time that I have observed and sketched this phenomenon.  It was a low contrast feature, yet very interesting.  To the right of my sketch is an image from Mr. Thomas Ashcraft in New Mexico, taken shortly after my observation.  His image is reversed E-W from my sketch, and both show the Polar Crown:

Overall, the sun is not very active, however, there is an area of activity rotating into view in the northeast.  In both my sketch and Thomas' image, you will notice a small area of plage, in the northern hemisphere just east of the central meridian.  This little area is termed an "ephemeral region" and likely has a lifetime of a day or less.  This ephemeral region of hydrogen alpha emission is also visible on these images from the new Solar Dynamics Observatory which is now posting daily images:

No comments:

Post a Comment