APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25)

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Expand view Topic review: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25)

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Ann » Wed Sep 28, 2011 12:10 am

I forgot to say thanks you to nstahl and Rob for explaining the difference in size between the Earth's surface and the Sun's. Rob, thank you for your traditionally coloured large "sueare of a Sun" compared with the tiny blue dot of the Earth!

And thank you, nstahl, for your compliment!

Art, you said something that I somehow missed the first time I read it:
The sun is indeed a wideband photospheric light source with the exception
of numerous narrow dark chromospheric Fraunhofer lines including the red 656.281nm Hα line.

While the (~5800 K) photosphere also radiates red 656.281nm Hα line that photospheric radiation
is all absorbed by the chromosphere which then re-radiates its own red 656.281nm Hα line
in accordance with its own (mostly colder ~ 4500K) temperatures.

It is only these colder darker chromospheric Fraunhofer lines that we can observe.
How interesting! Does that mean that the Ha radiation at 656.281nm that the chromosphere receives from the photosphere and then re-radiates is longer than 656.281nm? And if not, why not? I thought that is how it works. A hydrogen atom receives an ultraviolet photon from a hot surface (typically an O- or B-type sun) and re-radiates that energy as a red 656.281nm photon. Or an oxygen atom receives an even "harder" ultraviolet photon from a very hot source, say the central star of a planetary nebula, and re-radiates it as a photon whose wavelength is about 502 nm.

Therefore, if the chromosphere receives 656.281nm photons from the photosphere, shouldn't it re-radiate this energy at even longer wavelengths, probably in the infrared part of the spectrum?

Or maybe the chromosphere doesn't re-radiate the Ha light from the photosphere at all, but rather the chromosphere is inonized by ultraviolet light from the photosphere and re-radiates this ultraviolet light as its own 656.281nm photons?

Now that makes a lot more sense.

Ann

Ann

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Beyond » Mon Sep 26, 2011 5:53 pm

Well, that's an interesting thing. I wonder what it would look like when the shock wave came together on the other side of the sun? Perhaps one day we will be fortunate enough to get a video of the result of one occurring on the other side of the sun that we can't see starting, but can see finishing on this side of the sun. Keep them cameras rolling fellas!!

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by hdneuf@mts.net » Mon Sep 26, 2011 1:24 pm

Your caption says the tsunami 'circled the entire sun in . . . minutes'. But at a million km/h would it not take about 4 hours, given that the circumference of the sun is about 4 million km? Or about 2 hours for waves travelling in opposite directions to meet on the opposite side of the sun?

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by owlice » Mon Sep 26, 2011 3:03 am

Most of the "dark subtropic high dry spot" is outlined in a thin red line here (in a rectangle; I don't have good editing software at the moment. Click on the image to make it larger.):
dark.jpg
I don't know what you are looking at, but the "dark subtropic high dry spot" is the DARK PART of that image that is over the Pacific.

(At least, that's what I got out of neufer's post; if I'm wrong, I'm sure he'll correct me!)

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Ann » Mon Sep 26, 2011 2:27 am

Thanks, Owlice! You're right of course. That's South America in that image, not Africa. It just goes to show how basically similar in shape these two continents are - score one for plate tectonics! (Or else it tells you something about me. Whatever.)

But the Galapgos Islands are still in the Pacific, and it still looks to me as if the dark atmospheric "crescent-shape" in that image is over the Atlantic Ocean.

Ann

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Beyond » Mon Sep 26, 2011 2:00 am

Owlice, that's only if you remember where they are in the first place. I didn't. I was going to ask, but i figured someone else would. So now i know that there are at least two who couldn't remember. Hey, it's a big world with lots of stuff in lots of places. That's why at any given time, anyone can be dumb and forgetful about 'something'. I just wish i wasn't - so often. Oh-well, that's what you guys are for. :mrgreen:

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by owlice » Mon Sep 26, 2011 1:44 am

Yes it can, in this image:

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Ann » Mon Sep 26, 2011 1:28 am

Thank you for your very interesting posts, Art.

There is one small thing I don't understand. You wrote:
GOES hemispheric water vapor maps invariably have a pronounced dark subtropical high dry spot south of the Galapagos:
Image
The only "Galapagos" I know of are the Galapagos Islands, off the coast of Equador: :arrow:


But Equador and the Pacific Ocean can't be seen at all in the images you posted, not even as outlines superimposed on the opaque infrared water vapor cover of the Earth.






Ann

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by saturn2 » Mon Sep 26, 2011 12:43 am

The Tsunami Shock on the Sun.
This is a peculiar phenomeno. very interesting.

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by neufer » Sun Sep 25, 2011 9:21 pm

Nantee wrote:
orin stepanek wrote:
APOD Robot wrote:

The solar tsunami spread at nearly one million kilometers per hour, and circled the entire Sun in a matter of minutes.
Wow! That's about 278 kilometers per second. It's hard to imagine that kind of speed! :shock:
Wow, for what effectively is a sound wave to travel that fast, what would the density of the photosphere need to be? I'm thinking that since the speed of sound in air at sea level is roughly 340 m/s, that makes the density of the photosphere roughly 800 times denser than the air we breathe.
Firstly, these are coronal waves impinging upon the chromosphere...it has NOTHING to do with the photosphere.

The speed of sound in a gas is roughly equivalent to speed of the average the gas molecule (which is proportional to the square root of the temperature divided by the mass of the gas molecule). The corona is ~4,000 times hotter than the earth's troposphere and its molecules are ~30 lighter than those of the earth's troposphere so one would expect sound velocities ~ sqrt(4,000 x 30) ~ 350 times faster in the corona than in the earth's troposphere. (We are really dealing with magnetohydrodynamics here, however, so this is just "ballpark.")
Nantee wrote:
But there must be something wrong with my 800x density figure, because density of air at room temp is roughly 0.0012g/cm3. Multiply that by 1400 makes the density of the photosphere 1g/cm3, which is as dense as water. And the speed of sound in water is roughly 1.5 km/s. I guess density and the speed of sound isn't a sort of linear relationship?

The speed of sound in a liquid or solid where the molecules are packed virtually "shoulder to shoulder" depends directly upon the compressibility of the liquid or solid and has little to do with the speed of sound in a gas.

All things being the same, however,
higher densities normally result in slower sound speeds (not faster speeds).

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by NoelC » Sun Sep 25, 2011 8:59 pm

First, thanks very much to Neufer for the enhanced descriptions of what we're observing on the sun.
Beyond wrote:So, NoelC, did you add the color so i could see what the picture description said, even though it wouldn't normally actually be visible that way?
The reason the image is shown in grayscale is that the imager behind the Ha filter just reads out luminance measurements and these are being presented as pixel values with Red = Green = Blue values - e.g., grayscale.

I loaded the grayscale animated GIF into Photoshop, applied a 100% density red photo filter layer to all frames, set the animation to repeat forever, and saved it back out. This yields pixel values of luminance in the Red channel only, with Green = 0 and Blue = 0.

What I posted was much like what you'd see with a color camera mounted behind a deep red Ha filter.

Since the red color of your display no doubt has a wider bandwidth than the deep red of a narrowband Ha filter, what I've done is still not quite what you'd perceive if looking through an Ha filter (along with some attenuation as well so you didn't burn your eyes), but it is closer than grayscale.

If you ever get the chance to observe the sun through a good solar telescope with an Ha filter, make sure to do so.

-Noel

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by neufer » Sun Sep 25, 2011 7:49 pm

bystander wrote:
RJN wrote:Cool image! Can you tell me where you found it? Which satellite took this image?
Was it a GOES like this APOD: http://apod.nasa.gov/apod/ap020323.html ?

Thanks for any help you can be.

- RJN
I seems to be an image from METEOSAT-9 (eumetsat.int) (ESA Version of GOES)
http://astrobob.areavoices.com/2011/03/ ... s-and-ice/
Bystander is right, as usual.

It was snitched from astrobob's website: http://astrobob.areavoices.com/2011/03/ ... s-and-ice/

GOES hemispheric water vapor maps invariably have a pronounced
dark subtropical high dry spot south of the Galapagos: It should be noted that these water vapor depictions (like many astronomy photographs) are actually
photo-negatives with the dark dry spots representing the regions of brightest infrared radiation.

This is in line with the traditional procedure of always having white (rather than black) clouds
although clouds do not radiate much infrared radiation radiation (and, hence, should be black).

H-alpha pictures of the sun are normal photo-positives with the hottest most radiant regions being the brightest.

Since the vertical temperature lapse rate in the chromosphere is negative, however, bright regions
in both generally represent local topographical 'mountains' of gas (water vapor or hydrogen respectively).

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by bystander » Sun Sep 25, 2011 6:12 pm

RJN wrote:Cool image! Can you tell me where you found it? Which satellite took this image?
Was it a GOES like this APOD: http://apod.nasa.gov/apod/ap020323.html ?

Thanks for any help you can be.

- RJN
I seems to be an image from METEOSAT-9 (eumetsat.int) (ESA Version of GOES)
http://astrobob.areavoices.com/2011/03/ ... s-and-ice/

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by RJN » Sun Sep 25, 2011 5:28 pm

Cool image! Can you tell me where you found it? Which satellite took this image?
Was it a GOES like this APOD: http://apod.nasa.gov/apod/ap020323.html ?

Thanks for any help you can be.

- RJN

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Nantee » Sun Sep 25, 2011 4:27 pm

Oops, sorry, make that "1400" in the second paragraph "800". But it doesn't really help my figures or understanding.

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Nantee » Sun Sep 25, 2011 4:25 pm

orin stepanek wrote:
APOD Robot wrote: The solar tsunami spread at nearly one million kilometers per hour, and circled the entire Sun in a matter of minutes.
Wow! That's about 278 kilometers per second. It's hard to imagine that kind of speed! :shock:
Wow, for what effectively is a sound wave to travel that fast, what would the density of the photosphere need to be? I'm thinking that since the speed of sound in air at sea level is roughly 340 m/s, that makes the density of the photosphere roughly 800 times denser than the air we breathe.

But there must be something wrong with my 800x density figure, because density of air at room temp is roughly 0.0012g/cm3. Multiply that by 1400 makes the density of the photosphere 1g/cm3, which is as dense as water. And the speed of sound in water is roughly 1.5 km/s. I guess density and the speed of sound isn't a sort of linear relationship?

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by Beyond » Sun Sep 25, 2011 4:12 pm

Thanks Ann & NoelC for the explanations. So i take it then, at least in the case of today's APOD, that a red filter was used as the best way to pick up the detail of the shock wave, but because only one filter was used, the picture looks like black & white, or grey.

So, NoelC, did you add the color so i could see what the picture description said, even though it wouldn't normally actually be visible that way?
The animation worked well as i came to it.

To us non-scientific, non-photographer types, some pretty strange things go on in the astrophotography department. That's why we usually just look at the pretty pictures and let it go at that. For me to get much deeper into anything, would result in my face being covered with the Egg Nebula. :lol:

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by neufer » Sun Sep 25, 2011 3:36 pm

NoelC wrote:
One can't even observe the photosphere in opaque Hα light.
Not sure I agree with or understand what you're saying, Neufer...

First off, isn't the photosphere of the sun a wideband light source? If so, it must certainly be emitting at least some light in the 656 nm wavelength.
The sun is indeed a wideband photospheric light source with the exception
of numerous narrow dark chromospheric Fraunhofer lines including the red 656.281nm Hα line.

While the (~5800 K) photosphere also radiates red 656.281nm Hα line that photospheric radiation
is all absorbed by the chromosphere which then re-radiates its own red 656.281nm Hα line
in accordance with its own (mostly colder ~ 4500K) temperatures.

It is only these colder darker chromospheric Fraunhofer lines that we can observe.
NoelC wrote:
Secondly, what do you mean by "opaque Hα light"? Those words don't seem to go together.
"Opaque Hα light" makes about as much sense as "blackbody radiation" does...i.e., all the sense in the world.

Absorption & radiation are really two sides of the same coin.

Transparent objects are invisible not only because they do not absorb (or scatter) light
but also because they are incapable of re-radiating their own light.

One can see opaque (non-transparent) objects not only because such objects
intercept the light behind them (and/or scatter some of the light landing on them)
but because re-radiate light out according to their own unique temperature.

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by NoelC » Sun Sep 25, 2011 1:55 pm

One can't even observe the photosphere in opaque Hα light.
Not sure I agree with or understand what you're saying, Neufer...

First off, isn't the photosphere of the sun a wideband light source? If so, it must certainly be emitting at least some light in the 656 nm wavelength.

Secondly, what do you mean by "opaque Hα light"? Those words don't seem to go together.

-Noel

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by neufer » Sun Sep 25, 2011 1:49 pm

APOD Robot wrote:Image A Large Tsunami Shock Wave on the Sun

Explanation: Tsunamis this large don't happen on Earth. During 2006, a large solar flare from an Earth-sized sunspot produced a tsunami-type shock wave that was spectacular even for the Sun. Pictured above, the tsunami wave was captured moving out from active region AR 10930 by the Optical Solar Patrol Network (OSPAN) telescope in New Mexico, USA. The resulting shock wave, known technically as a Moreton wave, compressed and heated up gasses including hydrogen in the photosphere of the Sun, causing a momentarily brighter glow.
[url=http://solar.physics.montana.edu/nuggets/2002/020208/020208.html]Moreton wave[/url] wrote:
<<The phenomenon of Moreton waves was first reported in 1960 from the legendary Lockheed Observatory. Y. Uchida in his 1968-1974 papers nicely explained Moreton waves as the intersection of coronal shock waves (due to a flare) with the chromosphere.>>
So what does this have to do with the photosphere of the Sun :?:

One can't even observe the photosphere in opaque Hα light.

(And it is really more like a sonic boom than a tsunami.)

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by NoelC » Sun Sep 25, 2011 1:43 pm

Beyond wrote:but the image is grey. I don't mean to be picky,yes i dobut grey is not any shade of red that i am aware of.
Here you go, Beyond. This should help visualize the filter color used a bit better (you may have to refresh or click on this to see the animation)...

Image

-Noel

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by NoelC » Sun Sep 25, 2011 1:37 pm

Wow, something so particularly violent so as to be noticed on the surface of what is essentially a runaway nuclear reaction already... Impressive!

-Noel

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by rstevenson » Sun Sep 25, 2011 1:31 pm

Ann wrote:... I'm a math illiterate, and I'm trying to figure out how much bigger the "surface" of the Sun is compared with the surface of the Earth. The diameter of the Sun is about a hundred times larger than the diameter of the Earth. Can anyone tell me how much bigger does that make the surface of the Sun, compared with the surface ot the Earth? (So that I don't have to look it up myself?)
From the site smartconversion.com...

Surface area of the Sun: 6.088 x 1012 km2
Surface area of the Earth: 5.100656 x 108 km2

If I correctly punched those numbers into my handy dandy calculator, that makes the Sun's surface area about 11,936 times larger than the Earth's.

Or, to make it graphical, as a pixelator should...
area.jpg
area.jpg (4.3 KiB) Viewed 11609 times
The area of the (traditionally coloured :mrgreen: ) Sun is represented by the square, and the small blue dot near the middle represents the area of the Earth to the same scale.

Rob

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by nstahl » Sun Sep 25, 2011 1:25 pm

Ann, once again a relevant and informative reply. Thank you.

Area scales as the square of radius or diameter (in general, length) so if the diameter of the sun is 100 times earth's, the area is 10,000 times earth's.

Re: APOD: A Large Tsunami Shock Wave on the Sun (2011 Sep 25

by orin stepanek » Sun Sep 25, 2011 12:15 pm

APOD Robot wrote: The solar tsunami spread at nearly one million kilometers per hour, and circled the entire Sun in a matter of minutes.
Wow! That's about 278 kilometers per second. It's hard to imagine that kind of speed! :shock:

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