28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

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28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

Post by p_zetner » Fri Jul 31, 2020 9:40 pm

Hi Everyone.

A rather late post of some spectroheliograms taken on July 28. My processing is quite slow, some of it reliant on my computer programming skills which are a little rudimentary! I could still polish up some of the image details but will save that for full disk views that I am working on. The AR is shown in four wavelengths, three different chromospheres. The sunspot itself is not particularly visible in H alpha or He D3 as expected for a view largely determined by high altitudes in the solar atmosphere. It is expected to be visible in H beta (some photospheric contribution here) but, surprisingly, is quite visible in Ca K3. The spectral resolution is about 0.3 angstroms so the Ca K3 line should have very little photospheric "contamination".

Thanks for viewing and hope you enjoy.
Peter.
Montage_AR12767_28Jul2020_lbls.png
Montage_AR12767_28Jul2020_lbls.png (602.17 KiB) Viewed 174 times



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Re: 28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

Post by Carbon60 » Sat Aug 01, 2020 5:58 am

Thanks, Peter. Interesting to see the different views at these wavelengths. The sunspot appears strangely fragmented into multiple cores in Ha compared with how it looks in Ca II K3 or H beta, or are those dark areas just ‘tufts’ of spicules. Hard to tell.

Beautifully done.

Stu.


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Re: 28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

Post by Montana » Sat Aug 01, 2020 9:21 am

Very nice indeed :bow :hamster: the plage in Helium D3 seems to match that of Halpha but not of CaK, all fascinating :)

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Re: 28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

Post by JochenM » Sat Aug 01, 2020 9:36 am

Very interesting, Peter. Thanks for sharing.


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Re: 28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

Post by marktownley » Sat Aug 01, 2020 12:08 pm

Always like your comparison shots Peter, they're excellent!


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Re: 28 July: Portrait of AR12767 in 4 Fraunhofer Lines.

Post by p_zetner » Fri Aug 07, 2020 5:50 pm

Thanks for your comments everyone.

Stu: That apparent "fragmentation" of the spot worried me a little. I thought there might have been some sort of glitch in acquiring the spectroheliogram. To investigate a little further, I generated a spectral series of spectroheliograms around H-alpha line centre. Here is an animation showing the result (wavelength offsets in angstroms are shown with positive values implying offsets to the red).
spectral-series1.gif
spectral-series1.gif (1.64 MiB) Viewed 53 times
You can see the isolated spot in the continuum (offset = -1.16 angstroms) and then the gradual appearance of some dark "mottles" around the spot which become more visible closer to the line core. I think these are legitimate chromosphere features but can't really identify what they are.

Cheers.
Peter



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