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Huge prom right now!


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Nice sketch @Roy Challen. I missed that one but saw quite a few other nice ones during the day. The detail around the ARs was very impressive although my seeing wasn’t very good.

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  • 4 weeks later...

Could I ask how big is a big prom? I have seen enough white light activity over the years to know a big/huge sun spot when I see one but I am relatively new to Ha so I don't have a handle on what is exceptional yet...and can you tell if some initial activity is going to take off into a big prom from how it looks or acts beforehand?

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Posted (edited)

Good question, and seeing as I started this thread, I'll try to answer it.

In my sketch above, the prom at middle left hand side is twice as 'tall' as the next tallest prom. Also, it would have extended past the narrow field of view of GONG images.

To me, that's huge. The end/top could be 100s of 1000s of km from the surface.

I don't know if it's possible to predict when a prom will appear on the limb, but when an active region looks extremely bright, something could well happen in a short space of time. But equally, it might not!

Edited by Roy Challen
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It can be quite easy to predict some proms.  The dark filaments are proms seen in plan elevation against the surface, if they survive to be seen at the edge they become proms.  When they are seen half and half during this transition they are known as filaproms.  Flares, often confused as proms by newcomers to Ha viewing are fast moving high energy events, much brighter than the general surface and usually of short duration.  I always recommend keeping an eye on any hotspots near the edge as being areas where sudden activity may occur.  All proms are huge by terrestrial standards, one the size of Africa would barely be seen from Earth.   🙂  

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The typical large prominence is around 100,000 km - ie the sort of prom we see often at times of significant activity like now. Every now and then there are much bigger proms - I remember one  that was around 300,000km. In February this year, the Solar Orbiter captured a giant prom on the far side which stretched 3 million km into space - equivalent of 250 Earths.

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33 minutes ago, Highburymark said:

In February this year, the Solar Orbiter captured a giant prom on the far side which stretched 3 million km into space - equivalent of 250 Earths.

There really needs to be a wow emoji in the "like" options!  That's gigantonormous.

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I don't think most proms have sufficient energy to result in CME.s.  It takes an explosive large scale outburst to be effective, the mass and the velocity need to be sufficient to overcome the huge gravity of the Sun's mass.  I really thought that the outburst last Thursday lunch time was going to produce a CME as it dispatched a large area at high velocity.  I watched it streaming outwards for nearly an hour but it gradually slowed down and faded before returning to the surface.      🙂 

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On 26/04/2022 at 13:56, Roy Challen said:

Had it been shown on GONG, it would have extended outside the field of view.

IMG_20220426_093353058~2.jpg

That would be around 30x, so Baader plossl was able to take the entire disk and then some? Did you have to move the scope to frame the entire prom?

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17 minutes ago, BGazing said:

That would be around 30x, so Baader plossl was able to take the entire disk and then some? Did you have to move the scope to frame the entire prom?

Yep, easily fit into the field of view. No need to move the scope. Even with an 18mm BCO, the whole disc fits...just.

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