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Quantum Leap
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| Joined: | Sat Jun 25th, 2005 |
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Posted: Sun Jul 10th, 2005 09:21 pm |
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| There is a lot of interest in the solid Sun and granted the pictures are fun. But, this aside, does anyone know why the Sun has a sharply defined shape if it is gaseous, why does it suddenly stop and not have a 'gradient' type edge/
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lyndonashmore
Administrator
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Posted: Mon Jul 11th, 2005 07:53 am |
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I haven't read all the words on the solid Sun site (just looked at the pictures - no comments please!) but no one seems to refer to the average density. This is 1400kg/m^3 almost one and a half times that of water (maybe its a liquid Sun - lava). On some forums they talk about an outer iron layer but I can't see that with this density.
why does the sun have an 'edge'? Maybe it is fuzzy but the scale of the pictures makes it hard to see.
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Follower of Science
Guest
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Posted: Wed Mar 8th, 2006 12:53 am |
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The answer as to why the Sun has a sharp edge is because it doesn't. As every fule kno, during a total solar eclipse, we see parts of the sun that are normally hidden by the light given off elsewhere.
The body of the sun emits light as a continuous spectrum because it is in a state known as 'optically dense'. In other words, light energy is not given a free path from the body of the sun because (for the most part) the plasma density is such that photons are re-absorbed before they escape. The probability of a photon escaping is highly dependent on the density and temperature of the plasma
As we move outwards from the sun and approach the surface, there is a relatively shallow area where the temperature and density of the plasma changes sufficiently that within a few hundred kilometres the likelihood of a photon escaping goes from practically zero to almost certain.
What this means is that there is a shallow zone where the vast majorty of light appears to be emitted, but the 'sun' itself is much bigger than this zone.
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Quantum Leap
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Posted: Wed Mar 8th, 2006 08:21 am |
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Thanks for that, 'follower of science' but doesn't that only explain the inner edge of the 'shallow area' where photons produced can, and do, escape?
during a total solar eclipse, we see parts of the sun that are normally hidden by the light given off elsewhere
But there is a discontinuity, between the outer 'edge' of the Sun and the corona (the bit we see in eclipses - reddish because of the Hydrogen?)
If light seen in the 'shallow area' has a 100% chance of escaping then why does it suddenly 'stop' (or at least change colour and brightness) so suddenly between it and the corona?
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Thomas
approved users
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Posted: Fri Mar 10th, 2006 10:07 am |
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The sharp edge is due to inelastic collision of protons with atoms in the solar atmosphere. This is related to an energy loss (i.e. a cooling) which basically results in all the gas above the level where individual atoms can exist falling down.
See my webpage http://www.plasmaphysics.org.uk/research/sun.htm for more.
Thomas
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lyndonashmore
Administrator
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Posted: Tue Mar 14th, 2006 10:01 am |
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Hi Thomas,
I like the idea of reversing the present theories - its not that the corona is hotter than it should be, it is the Sun that is cooler! Sun spots seem to fit in with your idea - sun spots are cooler and this is where the magnetic field lines concentrate. Are protons trapped on these lines colliding with the Sun's surface at a 'sun spot' and cooling it?
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Thomas
approved users
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Posted: Wed Mar 15th, 2006 12:38 pm |
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Lyndon,
I am still not quite sure about the nature of sunspots in this context myself. The fact that sunspots are darker for instance does, contrary to common opinion, not imply that they are cooler. The brightness of the radiative emission of a plasma depends almost exclusively on its density rather than its temperature. The plasma density in turn may be affected by the temperature, but not necessarily so (in particular not if the plasma is not in Thermodynamic Equilibrium). So what one can say here is that the plasma density in the sunspots is less than elsewhere, which may have something to do with the magnetic field reducing the number of protons (and electrons) that can get through the 'inelastic collision layer' into the photosphere (as suggested on my page regarding the Coronal Heating)
Thomas
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Michael Mozina
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Posted: Mon Nov 3rd, 2008 09:34 pm |
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Actually, it *does* have a very definite set of "features" that are much more "rigid" than photosphere plasma. The wavelength of light we observe in iron ion lines allow us to observe the more rigid features under the photosphere, as does that Doppler image from Alexander Kosovichev on the tsunami page of my website. The sun does have a number of outer layers of hot light plasma, but the features we observe in running difference and doppler images come from *beneath* the photosphere, as that Doppler image from Kosovichev demonstrates. The "wave" in the Doppler image move *over* the "rigid structure" below the wave, and the rigid outline of the surface below is undisturbed from the movement of the wave.
Last edited on Mon Nov 3rd, 2008 09:35 pm by Michael Mozina
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lyndonashmore
Administrator
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Posted: Fri Nov 7th, 2008 06:51 pm |
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Hi Michael.
I have seen your work and it is interesting.
Certanly to look at the Soho pictures it looks the sun is 'solid' - like Herschel said many years ago!
But could this be due to the temperature? The soho pictures chooses a temp and produce the pickies. in a symmetrical temp situation this could 'look' like solid.
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Michael Mozina
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Posted: Fri Nov 7th, 2008 07:37 pm |
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Well, there is an issue here of "rigidity/time" here to consider, particularly in "running difference" and Doppler images such as Kosovichev's video.
Plasma is typically 'mobile". The "structures" of the photosphere tend to rearrange themselves in approximately 8 minute intervals. These Doppler and RD images show a distinct "rigidity" pattern that is unlike 'ordinary" plasma patterns.
If you watch the Kosovichev video, the "structure" under the photosphere is relatively undisturbed by the movement of the wave through the photosphere. Plasma is typically quite "liquid-like" in it's movements, and that wave on the photosphere is evidence of the "mobile texture" of the photosphere of the plasma. Whatever that "structure" might be underneath that wave, it is much more "rigid" and "angular" in it's configuration. Why?
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lyndonashmore
Administrator
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Posted: Sat Nov 8th, 2008 07:17 pm |
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Do you have a link to "Kosovichev's video"?
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Michael Mozina
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Posted: Mon Nov 17th, 2008 04:57 am |
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http://www.thesurfaceofthesun.com/tsunami.htm
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Current time is 04:36 am | |
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