Sunspots and Active Regions.

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Floater
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Sunspots and Active Regions.

Post by Floater »

I’m hoping some of the knowledgeable people here can help me answer a question: basically, does an Active Region always have an associated sunspot visible in white light?

I’ve often observed in WL, especially when spots were more plentiful, but lately, mostly in Ha. Solar activity is much reduced recently, of course, but today I pointed my scope (Lunt 60 Ha, DS) at the welcome little AR 2073. After a while, I switched to WL (TV76 with Herschel wedge, 8-24 zoom) to see an expected spot and was surprised to see a featureless disc. No spot.

My question(s) is/are whether there is always a spot or whether AR 2703 is just a very weak AR and they do not necessarily produce spots, or whether the resolving power of my scope is not great enough to have seen the AR 2703 spot?

I have a similar thread running on Stargazers Lounge but thought I’d come to where the solar gurus live ... 🤗

Aye,
Gordon


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robert
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Re: Sunspots and Active Regions.

Post by robert »

Scope is fine, low activity and invisible in WL, as you say
SOHO images are useful... (although the WL is corrupted just now 15.00UT!)
https://umbra.nascom.nasa.gov/newsite/images.html
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Re: Sunspots and Active Regions.

Post by marktownley »

not always active regions with spots. This active region is just the decaying splurge of one that came round in february...


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Floater
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Re: Sunspots and Active Regions.

Post by Floater »

Thanks, Robert and Mark, for the replies. It’s surprisingly(?) difficult to find anything definitive in the Interweb/Wikiworld stuff I’ve hunted through.
I read that ‘sunspots often form in active regions’, which implies the spot is not a ‘given’. But, also, I’ve seen ‘in sunspot-producing active regions’ - which is ambiguous; are ARs always sunspot-producing or do only some ARs produce sunspots.
I also read that the formation of a sunspot ‘creates’ an active region. Does this mean that an active region cannot be created without a sunspot?
I’m leaning towards the supposition that some ARs are just too weak to show a spot in WL, although the ‘spot’ is there.
Have I got it right?


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Re: Sunspots and Active Regions.

Post by Montana »

In the chromosphere active regions can be seen for a few weeks before and after the spot groups are visible on the photosphere. Calcium K is very good for seeing potential new active regions (you see plage) and decaying regions, with plage visible for many weeks after the spots have decayed. Halpha will be similar.
Alexandra


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