What is the green-colored "Far side" image on the SWL front page really showing?

[Philalethes]

I was under the impression that it, as the title of the box would imply, shows estimated farside activity, but looking at it just now I realized that it looked oddly similar to the current part of the disc that is in view, and looking more closely that's definitely the case, considering both the current CH and the ARs on the right; I also noticed that it says "Earth-view". On the SDO data page there's no indication that this is really a map of the far side, although the two composites above are.

Am I just missing something really fundamental here, or is that image just showing the visible disc rather than any estimate of the far side? To me it seems like the purpose of it is more to show the map of the visible disc in terms Stonyhurst heliographic coordinates, as it says, which indeed is what it seems like it corresponds to (based on the current slight tilt of the northern hemisphere away from us).

Hopefully someone can clear this up for me.

Edited December 10, 2023 by Philalethes
typo

[tniickck]

1 hour ago, Philalethes said:

I was under the impression that it, as the title of the box would imply, shows estimated farside activity, but looking at it just now I realized that it looked oddly similar to the current part of the disc that is in view, and looking more closely that's definitely the case, considering both the current CH and the ARs on the right; I also noticed that it says "Earth-view". On the SDO data page there's no indication that this is really a map of the far side, although the two composites above are.

Am I just missing something really fundamental here, or is that image just showing the visible disc rather than any estimate of the far side? To me it seems like the purpose of it is more to show the map of the visible disc in terms Stonyhurst heliographic coordinates, as it says, which indeed is what it seems like it corresponds to (based on the current slight tilt of the northern hemisphere away from us).

Hopefully someone can clear this up for me.

it is view from stereo-a. it is currently passing near the earth so it shows us visible from earth side of the sun

for example in 2011-2017 (later the solar minimum started) you could see the farside activity of the sun cuz stereo-a was really far from earth. additionally, stereo gives us 4 different images in 284,304, 171 and 195 Angstrom and has 2 coronographs COR1 and COR2

btw there were other same Angstrom images from stereo-b until it stopped working. 

Edited December 10, 2023 by tniickck
typo

[Philalethes]

24 minutes ago, tniickck said:

it is view from stereo-a. it is currently passing near the earth so it shows us visible from earth side of the sun

I don't think that's correct. The one on the front page says "AIA", which is the SDO instrument, and it's the same as the one on the SDO page itself. I know there's a separate page for STEREO-A that you can go to from there, but it's not the one on the front page as far as I can tell.

Edit:

Ah, I think I understand now. It also says "EUVI", which is the STEREO-A instrument, so if I understand correctly it's a combination of both EUVI and AIA. That does make sense if that's the case.

[hamateur 1953]

@3gMike And me had nearly the identical conversation two weeks ago.
I asked him a hypothetical question where a large white area was contrasting with the green background on the Stonyhurst display.
assuming that it began at -90 degrees and extended back to -60 degrees could it be trusted to be an accurate representation of backside activity?  I’ m paraphrasing here. But it was Mike’s feeling that the image was distorted or stretched regardless, and he preferred to trust JSOC for a better assessment.    Edit. I wasn’t all that concerned with longitudes to a degree. Rather its display being relative anyway.  More as a general indication of activity per se. Guess I should have indicated this also. 

Edited December 10, 2023 by hamateur 1953

[Philalethes]

21 minutes ago, hamateur 1953 said:

@3gMike And me had nearly the identical conversation two weeks ago.
I asked him a hypothetical question where a large white area was contrasting with the green background on the Stonyhurst display.
assuming that it began at -90 degrees and extended back to -60 degrees could it be trusted to be an accurate representation of backside activity?  I’ m paraphrasing here. But it was Mike’s feeling that the image was distorted or stretched regardless, and he preferred to trust JSOC for a better assessment.    

As per the above, I'm pretty sure at this point that it's a composite of EUVI on STEREO-A and AIA on SDO; in other words, when STEREO-A was covering the far side you'd get coverage of the combined area the two covered, but now that STEREO-A is right next to us we're seeing virtually no far side activity on that map at all, only some slight coverage ahead of us. If you look closely you can see it cuts off at close to -90° on the left side, but extends a few degrees past that on the right side due to STEREO-A. Two weeks ago the situation would hardly have been much different, except even less coverage by STEREO-A on the right side, i.e. even more overlap.

I guess I'll mark @tniickck's answer as the solution even though it only mentions STEREO-A; maybe they meant in addition to SDO anyway.

Edited December 10, 2023 by Philalethes
typo

[tniickck]

32 minutes ago, Philalethes said:

I don't think that's correct. The one on the front page says "AIA", which is the SDO instrument, and it's the same as the one on the SDO page itself. I know there's a separate page for STEREO-A that you can go to from there, but it's not the one on the front page as far as I can tell.

Edit:

Ah, I think I understand now. It also says "EUVI", which is the STEREO-A instrument, so if I understand correctly it's a combination of both EUVI and AIA. That does make sense if that's the case.

yep, it combinates the earth-view and stereo-view so we get a full visible disk (if the stereo is directly opposite the Earth behind the sun) 

[hamateur 1953]

Good to know.  I was wondering about the shadow of that huge coronal hole being present on the display anyway.  I was pretty sure the hole didn’t go all the way through the sun.  Haha. 

[Philalethes]

17 minutes ago, hamateur 1953 said:

Good to know.  I was wondering about the shadow of that huge coronal hole being present on the display anyway.  I was pretty sure the hole didn’t go all the way through the sun.  Haha. 

Heh, yeah, that's exactly what my first thought was too. At first I thought, "hmm, that's weird, the CH seems to be mirrored on the far side...", but as I inspected it it became clear that it was identical and that something else was up.