Saturday Sun, Polar Faculae and Bright Points - 17th August

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Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by marktownley » Sun Aug 18, 2019 9:47 am

Saturday afternoon brought some brighter spells, we're in a westerly airstream coming off the Atlantic at the moment that brought long streamers of cumulus clouds, the alignment of these bands make all the difference; get stuck under one and it is overcast for sometime or get in between bands and lovely sunshine. As the edge of the bands got closer to the sun in the sky the seeing went down hill as instability with the rising airmass kicked in. So, very much a case of picking the moment to image.

First off a full disk with a Lunt50 etalon double stacked with a Daystar Quark, inspired by Stephanes lovely onband full disks I tried a click over on the Quark dial, which seemed to give me darker filaments on the disk. With these essentially blank disks it is tricky to drop on the tunung, I think i'm close with this.

ImageHa-FD-DS-bw by Mark Townley, on Flickr

ImageHa-FD-DS-colour by Mark Townley, on Flickr

At first sight the sun appears blank, but there is more going on than seems. First there is the small prom that viewer sketched earlier in the day viewtopic.php?f=4&t=26466 . Then we have a few filaments, most of these are mid latitudes in both hemispheres which indicates they are associated with sub surface magnetic jet streams of cycle 25. What was apparent to me though was the brighter mottling at both poles which are associated with polar faculae, which Pepe got in white light yesterday too viewtopic.php?f=4&t=26469

I think to understand what is going on it helps to look in other wavelengths, with AIA193 being a good choice:
latest_1024_0193.jpg
latest_1024_0193.jpg (137.7 KiB) Viewed 976 times
You can see at each pole there is a dark patch which is the polar coronal holes - an area where the magnetic field lines are weaker and it is easier for material to flow out into space. Here we see the polar faculae, magnetic flux regions that are not strong enough to form pores or sunspots. Polar faculae are dominant in solar minima conditions, where we are now, as the the poles magnetic fields are stable. During solar maxima we do not see polar faculae as the poles at this point undergo magnetic field reversal at this point of the cycle and so polar faculae are not able to form. I got a closer look of the northern polar region with the SM90 double stacked with the Quark.

Imagepolar-faculae-north-bw by Mark Townley, on Flickr

Imagepolar-faculae-north-colour by Mark Townley, on Flickr

The polar faculae show as bright points in white light on the photosphere, but here higher up in the chromosphere in Ha they look like little jets shooting upwards. The line of filaments on the bottom of the image is the cycle 25 jet stream, I like the little loop that is visible on the left!

Looking at the AIA193 image there are hints that both polar coronal holes are showing signs of a tenuous link, however on the departing limb by the equator a rash of bright points were visible. These are indicative of cycle 24 activity, but were easily seen.

Imageplage-w-limb-bw by Mark Townley, on Flickr

Imageplage-w-limb-colour by Mark Townley, on Flickr

Would have liked to have taken more images, however took a load of data and this was what was usuable, rest was soft and chucked away. Hoping to get a few more images today too weather behaving again!

Hope you like.

Mark


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by xn44 » Sun Aug 18, 2019 10:09 am

Thanks, your explanations help a lot to understand the reality of our star.



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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by MAURITS » Sun Aug 18, 2019 2:54 pm

Nice FD Mark.


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by ffellah » Sun Aug 18, 2019 4:42 pm

Beautiful images and very instructive commentary, Mark. I learned something new today. Thank you !

Franco



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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by marktownley » Sun Aug 18, 2019 6:04 pm

Thanks guys! :)


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by Valery » Mon Aug 19, 2019 4:05 am

What we really want to see on your images - are the cycle-25 quite certain signs !

Nice images, Mark


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by Carbon60 » Mon Aug 19, 2019 5:31 am

Good information, Mark and nice images.

Stu.


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by Montana » Mon Aug 19, 2019 9:19 am

Superb images Mark and a thoroughly interesting narrative, I always look forward to your posts :bow :bow :hamster:

Alexandra



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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by eroel » Mon Aug 19, 2019 3:05 pm

Mark:
Thanks for the info and for the clean crisp shots.
Regards,
Eric.



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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by marktownley » Mon Aug 19, 2019 3:20 pm

Thanks everyone for the kind words! Thunder and lightning today, so did some more ebay selling instead of solar...


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by krakatoa1883 » Mon Aug 19, 2019 3:22 pm

Fine images, Mark. I too use my Quark to darken filaments through my Lunt-mod scope, my results depend much on finding the best matching tuning of both systems, not always easy to do.


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by Starry Jack » Tue Aug 20, 2019 12:02 am

Agreed: Beautiful shots and informative narrative.


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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by allhoest » Tue Aug 20, 2019 5:29 am

Thank you Mark for your nice explanation.
Detailed pic also.
CS
Ale



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Re: Saturday Sun, Polar Faculae and Bright Points - 17th August

Post by MapleRidge » Wed Aug 21, 2019 1:43 am

Very nice session Mark...these images came out very well :bow

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