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Chromospheric layer in CaK?

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#26 marktownley

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Posted 01 June 2013 - 04:18 PM

Thanks Harald & Bob.

Here is one of the initial frames I took when I realised what O was seeing. I was imaging at 3200mm fl for this shot with the 100mm frac when I realised I needed to back off to 2000mm for the animation shots just to get it all in.

Mark

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#27 BYoesle

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Posted 01 June 2013 - 08:25 PM

Totally awesome images/animation Mark! The prominence dynamics are splendid - thanks for posting :bow::bow::bow:

#28 marktownley

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Posted 02 June 2013 - 04:36 AM

Thanks Bob,

Here is a shot of the same area a day earlier (30th may)

Mark

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#29 marktownley

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Posted 02 June 2013 - 04:39 AM

And the Ha shot from the same time for comparison...

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#30 BYoesle

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Posted 15 July 2013 - 04:48 AM

For the CaK afficionado: I found the diagram below in Foukal, P.V. (1990) Solar Astrophysics (p. 309). New York: Wiley & Sons. It shows the diagram referred to by John Varsik above, and now it is easy to visualize his discription...

You can download the CaK absorption line spectra online to see the K1, K2, and K3 parts of the line. I have one, but cannot attach it.

The line at 3933 angstroms is called K because that's what Fraunhofer called it. The K1, K2 and K3 refer to specific parts of the line. The K line is very dark and wide, but at the center of it is an unusual "brightness reversal" -- the center of the line gets brighter. The very core of the line reverses again -- there is a dip in brightness again. The line arises from a transition between the 4p 2P 5/2 state to the 4s 2S 1/2 state (really need sub- and superscripts to write these correctly) of singly ionized calcium (Ca II). The Ca II K line is one of the most useful lines in the solar spectrum, but it is one of the most complicated lines in terms of its formation.

K1 = the point in the line wings where the reversal starts. There are two
points, called K1R and K1V on each side of the center of the line.

K2 = the point of maximum brightness in the reversal. There are two points, K2R
and K2V again on each side of the center of the line.

K3 = the dip at the very center of the line.

Note that in high resolution spectra the whole line (or parts of it) can be
Doppler shifted and thus vary in appearance depending on what's happening at that location on
the Sun.

These portions of the line arise at different heights in the upper photosphere
and chromosphere. K1 comes from near the temperature minimum, K2 from around1000
km above that, and K3 from higher in the chromosphere. See Mihalas' book Stellar Atmospheres pg. 380 for the gory details.

John Varsik
BBSO

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#31 ch-viladrich

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Posted 25 July 2013 - 05:03 AM

Hi,
This is what is called the chromospheric "fringe". It can be seen in various wavelenghts (Ha, Ca K, etc).
One very interesting project is to measure the height of the fringe along various diameters of the sun and over the solar cycle.
In fact, the shape (the oblateness) of this fringe varies along the solar cycle, probably following the solar magnetic field variations. There is very little data on this variation.

I have been trying to follow these variation for some years. Not an easy task ... Here are for example some pictures taken in 2011. Unfortunatly, the Ca K filter I use gives a very faint fringe. Look at the "chromo fringe" link on this page :
http://www.astrosurf.../soleil2011.htm

#32 Vince22

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Posted 26 July 2013 - 01:08 AM

Hi All !!

I found this ....

http://adsabs.harvar...O&T....74....2B

Ciao

#33 ch-viladrich

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Posted 26 July 2013 - 10:51 AM

Serge Koutchmy (Astrophysical Institute of Paris) has been working on this interesting subject for some years.
See for example :

http://link.springer...0860.pdf#page-1

http://adsabs.harvar...A&A...464.1119F

http://arxiv.org/ftp...8/1208.4476.pdf

#34 sullij1

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Posted 26 July 2013 - 09:18 PM

Wow, great shots. I can't believe I am reading the papers. I get nerdier by the day. :smirk:

#35 George9

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Posted 26 August 2013 - 01:20 PM

Thanks Andy & George - would love to see what you find out George...


Bob, I did finally get an ideal opportunity to compare the position of a sunspot that was very near the edge on band and off band in H-alpha on 8/24/2013. The spot had a thin line of brightness between it and the photospheric edge when observed off band. Dialing to on band with DS, the distance to the edge was appropriately larger. Going to SS, it confirmed it by showing both, although right above the spot, the chromosphere seemed to come down toward the photosphere a little and might explain the images in this thread.

George

#36 BYoesle

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Posted 27 August 2013 - 12:39 PM

Thank you George, I really appreciate the interest and confirmation. I have been kind of swamped lately...

#37 Arne Danielsen

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Posted 28 August 2013 - 12:08 PM

Gorgeous and inspiring animation, Mark!

Best regards,
Arne






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