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What goes around... how do we know if sunspots return?

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#1 Spot On

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Posted 21 January 2021 - 11:03 PM

Today I was looking at AR2797 and AR2798 in look strangely familiar in Helioviewer after editing pictures taken on December 29, 2020. Helioviewer has handy time increment called a "Carrington rotation".  If I wind the clock back one rotation, it's uncannily similar:

 

Today:

2021_01_22_01_30_23_HMI_Int.jpg

 

One Carrington rotation back:

2020_12_25_18_54_00_HMI_Int.jpg

 

So my question is: how do we know that AR2797 and AR2798 are different from the prior sunspot group?  And who makes that decision!

 

Clear stable skies

Scott



#2 TOMDEY

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Posted 22 January 2021 - 12:32 AM

Well, to be entirely scrupulous, it would have to be satellites that observe "the back side" of the sun when we can't see it. I don't know that any such satellites exist... but that would be a fun thing to have. Extending the obsessive concern even further... some notable ancient philosophers used to seriously wonder whether today's sun is the same sun that they saw yesterday... or whether the gods switched it for a fresh one, just to toy with our little minds, for their everlasting amusement. We no longer have that concern, because people on the other side of the world make sure that the gods don't screw with things when Athens is in darkness.

 

To make things even more disturbing, quantum physicists seem to have proven that unobserved particles become indeterminately unreal when no one is looking.    Tom


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#3 chemman

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Posted 22 January 2021 - 01:23 AM

The actual gyrations that the sun goes through during the 9 days it takes for us to see the same face is disturbing.  I would like to think there are some "satellites"  that monitor the sun 24/7/365 from all directions.

 

Chuck


Edited by chemman, 22 January 2021 - 01:25 AM.


#4 Spot On

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Posted 22 January 2021 - 02:22 AM

The actual gyrations that the sun goes through during the 9 days it takes for us to see the same face is disturbing.  I would like to think there are some "satellites"  that monitor the sun 24/7/365 from all directions.

 

Chuck

That was the goal of STEREO, and for a long time you could get a full-globe image of the sun from there. But STEREO B died a few years ago and A is ailing. So AFAIK we are limited to the helioseismological farside images from GONG, but those seem pretty noisy.



#5 MalVeauX

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Posted 22 January 2021 - 06:34 AM

Heya,

 

It's hard to know without direct continuous observation; so it makes sense that we renumber them as the make a 2nd transit facing us.

 

In this above example though, it's been a month. The transit of a region on either side happens in less than half that time frame, so it would have already happened a while back and this wouldn't be it just based on time.

 

Very best,



#6 Spot On

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Posted 22 January 2021 - 01:47 PM

Heya,

 

It's hard to know without direct continuous observation; so it makes sense that we renumber them as the make a 2nd transit facing us.

 

In this above example though, it's been a month. The transit of a region on either side happens in less than half that time frame, so it would have already happened a while back and this wouldn't be it just based on time.

 

Very best,

I can see where you're coming from around renumbering.  For the purpose of space weather monitoring, it's not relevant whether it is the same sunspot or not.

 

The Carrington rotation period is 27.5 days, so if we see the same thing in 27.5 days in relatively the same position (transit across the visible side approximately half that), it seems likely that it's at least related.  Of course the Carrington rotation period is empirical based on sunspot, so to a certain extent it qualifies as a self-fulfilling prophecy. I'll have to review some old STEREO data.

 

Clear steady skies!




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