What disk? From SDO's perspective the sun is a giant "disk" in the sky. That disk! This disk in a long cadence RD image:
The red/orange flaming ring is the chromosphere in SDO.
What do you mean by "on" and "inside"?
The limb darkening is *INSIDE* of the chromosphere. Likewise the RD image will reside *INSIDE* of that chromosphere. If we were to look at a full disk image, it will show up inside that red/orange region with 4800KM to spare. It will be physically and directly related to that limb darkening region.
Let's recap for the newbies now. You have a green "opaque" math bunny problem in the SDO images. If I had access to the FITS files, I would/could turn off the blue iron line in the original release image and demonstrate to you that you have a yellow math bunny problem. I'd then turn the blue line back on and demonstrate your bunny turns green again. I would then turn off the yellow line and turn your bunny blue. I would then turn the yellow line into a red line and make your bunny glow a pretty purple. Alas I can't play with your color bunnies because I can't access the FITS files yet.
The more "decisive' way to demonstrate this point is with the RD images. If the SSM is correct, all those iron line emissions *MUST* start above the chromosphere ring, and the RD image outline should end up right along that red orange ring. If however the iron emissions start at the limb darkened region as I believe they do, then the RD image will show a disk that fits nicely inside that red/orange ring with 4800 KM to spare.
There are technically two different RD techniques we might use. We could use a longer cadence version to find the edge of the disk to see if aligns itself with the chromosphere or the limb darkened region. The second and "better" way to go about it IMO would be to round up the higher cadence/averaged RD process that created this image:
Apply that process to the 171A channel of SDO. Then lay that chromosphere on top of that image. That will/would be one of *THE* most spectacular images of the sun for all time IMO. It will also demonstrate that the iron line emissions originate in the limb darkened areas, not at the chromosphere boundary. Of course those green bunny problems should have already told you all of this, but then denial seems to be the name of the game around here. "What disk"?
