whats the story about helium D3 line?

I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!
Post Reply
highfnum
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 1207
Joined: Sat Nov 24, 2012 2:33 pm

whats the story about helium D3 line?

Post by highfnum » Mon Dec 08, 2014 4:21 pm

I notice a few shots in the helium line
what is significance of this line?
where is it exactly I know its near sodium

User avatar
Merlin66
Librarian
Librarian
Posts: 3093
Joined: Tue Dec 13, 2011 1:23 pm
Location: St Leonards, Australia
Contact:

Re: whats the story about helium D3 line?

Post by Merlin66 » Mon Dec 08, 2014 9:03 pm

http://adsabs.harvard.edu/full/1964ZA.....60..207B
To quote:
- It is absent in the normal solar spectrum
- Can flare in absorption or emission
- produced by a different mechanism to Ha

Since it's discovery in 1868 the D3 was thought to be a new element - Helium. It was only in 1895 that the gas was finally identified.
Hope this helps.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17951
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Contact:

Re: whats the story about helium D3 line?

Post by swisswalter » Tue Dec 09, 2014 5:16 am

Hi Ken

an interesting story
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

User avatar
p_zetner
Almost There...
Almost There...
Posts: 736
Joined: Sun Mar 18, 2012 4:59 pm

Re: whats the story about helium D3 line?

Post by p_zetner » Tue Dec 09, 2014 4:27 pm

The He I D3 Line is somewhat of a favourite of mine!

Here are some of the facts I'm familiar with.
Line Centre: 5875.7 Angstroms.
Linewidth in absorption features (plage regions) is ~ 0.5 Angstroms fwhm.

This line is generally invisible on the solar disk (absorption is too weak) except in regions of plage and filaments where absorption is enhanced. The correlation between He absorption features and H alpha features can be seen in the spectroheliograms I posted here in July 2014:

http://solarchat.natca.net/viewtopic.php?f=8&t=12392

The line is very bright at the limb and in prominences. There is a bright D3 limb "band" visible in telescopes with very high angular resolution. Measurements show that this band corresponds to He D3 emission from a shell with a sharply defined lower edge about 1400km above the photosphere.

The mechanism of He D3 absorption is interesting (to me!). Extreme ultraviolet (EUV) radiation from the corona shines downward, illuminating the He from above. This EUV light is energetic enough to ionize the He. Recombination of the ions and free electrons then produces neutral He in excited states of high excitation energy (~20eV) from which we see absorption at the D3 line as well as the He IR (10830 Angstroms) line. The observed shell in limb emission is consistent with this idea. The bottom of the shell corresponds to the maximum depth that the coronal EUV radiation can penetrate (downwards). Also, because radiation from the corona is required, He D3 absorption features don't appear where coronal holes are present. He IR images are used as "proxy" maps of coronal holes, the only tool to map coronal holes from the ground. I guess He D3 images could serve the same purpose but the D3 absorption is much weaker than the IR absorption. Here is a comparison of one of my He D3 images with a professional He 10830A IR image:

http://solarchat.natca.net/viewtopic.php?f=8&t=11761

As opposed to other chromospheric gases, He is optically thin and can be used (in emission, at the limb) to measure chromospheric magnetic fields by a phenomenon called the Hanle effect. The Hanle effect is responsive to much weaker fields than the Zeeman effect and such measurements have given the first accurate picture of chromospheric magnetic fields.

Finally, the D3 line has also been used as a diagnostic of solar flare dynamics. The additional information this line provides is of great interest to the experts but beyond my understanding, at the moment.

Cheers.
Peter.
Last edited by p_zetner on Tue Dec 09, 2014 4:58 pm, edited 2 times in total.

highfnum
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 1207
Joined: Sat Nov 24, 2012 2:33 pm

Re: whats the story about helium D3 line?

Post by highfnum » Tue Dec 09, 2014 4:40 pm

thx for replies

if you don't normally see line how did you record it?

User avatar
p_zetner
Almost There...
Almost There...
Posts: 736
Joined: Sun Mar 18, 2012 4:59 pm

Re: whats the story about helium D3 line?

Post by p_zetner » Tue Dec 09, 2014 4:44 pm

One of the image processing steps involves subtracting an on-band image from a nearby continuum image.

Derek Klepp
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 12506
Joined: Wed Oct 19, 2011 10:02 am

Re: whats the story about helium D3 line?

Post by Derek Klepp » Tue Dec 09, 2014 8:39 pm

Peter and Ken thanks for the explanations.

User avatar
swisswalter
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 17951
Joined: Thu Feb 06, 2014 4:28 am
Location: Switzerland
Contact:

Re: whats the story about helium D3 line?

Post by swisswalter » Tue Dec 09, 2014 9:06 pm

Hi Peter

thank you very much for the explanations. I love that stuff
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

User avatar
marktownley
Librarian
Librarian
Posts: 23807
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Contact:

Re: whats the story about helium D3 line?

Post by marktownley » Tue Dec 09, 2014 11:30 pm

Great info folks!
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

User avatar
Marcello
Im an EXPERT!
Im an EXPERT!
Posts: 375
Joined: Sat Dec 28, 2013 5:06 pm

Re: whats the story about helium D3 line?

Post by Marcello » Fri Dec 12, 2014 10:52 am

Hi Peter,
this is very interesting and your explanation very clear, thanks!
Play in the sunshine, we're gonna get over !!

https://www.flickr.com/photos/87718267@ ... 5844277683

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest