these darker regions seen on STEREO HI1 have been seen many times before.

they are areas of subtraction
[link to stereo.gsfc.nasa.gov]
"dark regions caused by an imprecise background subtraction. These dark regions should be filled in when the image is reprocessed after 35 days."

here are a few images from earlier in the year where we can see the same "dark" regions on STEREO HI1
[link to stereo.gsfc.nasa.gov]
[link to i.ytimg.com]
[link to img140.imageshack.us]
[link to i.ytimg.com]

i would post the info on the posted thread, but i dont feel like being called a Shill today ;)