Penumbral Waves!

Late November Sun

My last solar observing day for 2011 was November 25, just 28 days from the winter solstice. The Sun manages a maximum altitude of only about 30 degrees above the horizon at this time of year and is mostly hidden behind trees and rooftops from my observing spot. Even though a small two hour window between trees still exists, the colder weather discourages me. My tolerance for winter observing has been severely diminished by 33 freezing years spent in the unheated Randolph College observatory. I probably won't observe again until March or April.

It was unseasonably warm and pleasant on November 25, so I made the most of my brief view between trees. First, look at this mosaic of sunspots and filaments:

Sunspot 1358(L) and the 1356 group(R) (Click for full detail)

Moving across the Sun to the right of the mosaic above brings sunspot 1355 into view to the right of the 1356 group along with a nice set of filaments:

Sunspot group 1356(L) and sunspot 1355(R) (Click for full detail)

After completing the still images I tried, once again, to make some movies. Seeing conditions were fairly good in spite of occasional wind. Once again I failed to record any extremely dramatic eruptions, but I did manage to capture examples of a phenomenon known as penumbral waves. The first movie below shows 60 minutes of action in sunspot group 1356 from 12:16 PM to 1:16 PM EST. (Be patient until the movie loads and plays properly.) An eruption spewing out a gas plume was already in progress on the far left as recording began. Focus attention on the largest dark sunspot umbra and the lighter grey penumbra surrounding it. You will notice circular ripples heading out from the center like waves from a stone dropped in a pond. These are called penumbral waves.

Penumbra waves were also visible in sunspot 1355 below during the same time period: