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

[owlice]

Yes it can, in this image:

Click to view full size image

[Beyond]

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.

[Ann]

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

[owlice]

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.):

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!)

[hdneuf@mts.net]

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?

[Beyond]

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!!

[Ann]

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