How fast visually can prominence eruptions be seen to move?

[Elp]

Taking the Coronado PST out today, I'm sure I saw two prominence eruptions from off centre towards the right of the sun and shoot right out of the field of view literally within seconds of each other. The matter moved out of view in less than half a second. Did I imagine it?

Edited August 1, 2022 by Elp

[Roy Challen]

Hmm, interesting question. I have watched proms extend from the limb out to about 3x earth diameter (very rough guess) in 20 mins or so, giving a very approximate speed of 100,000km/h. Assuming a perpendicular line of sight and that it is an average event,  I guess it's entirely possible to reach even higher speeds. Without knowing your TFoV, would be hard to have a guess at what you saw.

Edited August 1, 2022 by Roy Challen

[Elp]

I was using a WO 15mm swan 72 degrees fov? The whole sun fits into the fov. I've dismissed any internal reflections as the WOs give excellent ha views, more so than other plossls like TV (20, 30) and ES (6.7 too much for the PST).

Edited August 1, 2022 by Elp

[Roy Challen]

According to astronomy.tools, a 15mm WO swan in a PST gives a true field of view of 2.7 degrees equating to approximately 7 million km at the distance of the sun. For something to leave the sun and disappear from the field of view in 0.5 seconds, it would have to be moving at...ludicrous speed😉. So, either my maths is utter rubbish (very possible), or you saw something that didn't originate from the sun.

Edited August 2, 2022 by Roy Challen

[Rusted]

Perhaps the problem of high velocity should be examined from an alternative viewpoint?

Was there any recorded prominence activity at the time of the observation?

The sun is under fairly constant scrutiny. All it needs is the UT of the observation.

UTC + 1 for British Time. If we can assume that "Elp" is viewing from Britain.

[MalcolmM]

I sometimes think I see proms come and go in suspiciously fast times. I am pretty sure most (or all) of them are combinations of variations in seeing and the observed area moving in and out of the Lunt 50 sweet spot.

I have seen genuine changes (I think!) over periods of 10 or 15 minutes.

Malcolm 

[Stu]

I would agree with others that the changes I’ve seen tend to be over periods of minutes not seconds. I’ve seen ‘blobs’ (technical term) of plasma raining down into the surface over a few minutes, and sometimes large spicules forming and disappearing quickly. I’ve not seen a full blown CME type event but even these would likely take longer than seconds, simply because of the huge distances involved.

I did some quick research, and from what I can see, the maximum speed for proms is between 600 and 1000 km/s. The Sun is approximately 1.3 million km across, so by my reckoning a prom would take 1300000/1000 = 1300 seconds or 21 minutes to move a distance equal to the diameter of the Sun.

A typical prominence is 100,000 km tall, with the biggest up to 500,000km, which equates to 100 seconds or 500 seconds (just less than two minutes to just over 8 minutes) for the plasma to travel that far.

If you think about it, if something travelled say 300,000 km in a second, that is basically the speed of light, so is out of the question unless my maths is worse than I thought 🤪🤣.

[Elp]

Guess it was my imagination. Solar viewing takes some work I must say, you really need to concentrate your vision and usually in the boiling heat to boot.

[Rusted]

Flares can appear very quickly and be gone again.
I tend to catch them due to my rapid capture technique when imaging.
Lots of short videos. While live processing the last capture.
No doubt there is some velocity involved with flares but it is mostly line of sight.

My gut feeling would be internal reflections for rapid prom movements beyond the limb.
I do so little visual observing these days. Unless you count watching a huge H-alpha sun in B&W on a 27" HD monitor.
No doubt there is a name or acronym for that these days. AMSR? Augmented Monochrome Solar Reality? 

[Peter Drew]

I visually observe the Sun in Ha with a 6" refractor with a minimum of 150x magnification.  I sometimes think I can see real time changes in the shape of active proms and specially plasma globules as they change brightness, these appearances are often reported by others.  However, an object on the Sun's surface travelling at the speed of light would still take several seconds to travers the disc so visual real time movement is probably an illusion.  It's similar to watching the movement of the minute hand of an average clock, you can almost see it move but lose concentration or look away for a moment and it has moved.    🙂

[Highburymark]

I’ve seen plasma moving in real time twice in many years of solar observing - that’s twice in around a thousand sessions, so it’s very rare. One was an X-class flare earlier this year. And I think both were at magnifications of 140-150x. But as Peter describes, much of the movement was perceived in relation to other comparatively static features around the rapidly expanding plasma - like an area of background space becoming smaller in size, which could be seen in real time. 

[Dan Sheppard]

As far as math calculations are concerned, I am a retired Certified Public Accountant and should no longer come near mathematic calculations. 😜

[Rusted]

45 minutes ago, Dan Sheppard said:

As far as math calculations are concerned, I am a retired Certified Public Accountant and should no longer come near mathematic calculations. 😜

Nobody's perfect. 😉