Collision-dominated plasma (stellar coronae)

  • #1

Summary:

I was reading some astrophysics paper, they said "Collision-dominated plasmas (e.g. stellar coronae), photo-ionized plas-mas (e.g. AGNs) or transient plasmas (e.g. SNRs) are considered."
Does anyone know what is the difference between these plasmas? for example, temperature, density, charge state etc.
Naively, "collision-dominated " means like ion-atom charge exchange is dominant ?

Main Question or Discussion Point

The paper is "Helium-like ions as powerful X-ray plasma diagnostics"
Proceedings of “X-ray Astronomy 2000”, Palermo, Sep. 2000
ASP Conference Series, Vol. TBD (in press), 2001
R. Giacconi, L. Stella, S. Serio
[Mentors note: arXiv link at https://arxiv.org/abs/astro-ph/0012218v2]

By the way, why the resonant emission, intercombination emission and forbidden emission of He-like ions are very diagnostical tool for high temeprature plasma?
 
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Answers and Replies

  • #2
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I'm not an expert but collision dominated sounds like a thermal plasma (i.e. in thermal equilibrium) and photoionized sounds like non-thermal.
 
  • #3
mathman
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Presumably "collision dominated" plasmas have higher density.
 
  • #4
I'm not an expert but collision dominated sounds like a thermal plasma (i.e. in thermal equilibrium) and photoionized sounds like non-thermal.
could you explain more what you mean " thermal plasma (i.e. in thermal equilibrium) and photoionized sounds like non-thermal. "?
 
  • #5
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could you explain more what you mean " thermal plasma (i.e. in thermal equilibrium) and photoionized sounds like non-thermal. "?
I'm just guessing really.

Normally, in a gas say, high rate of collisions leads to thermal stability or local thermodynamic equilibrium, as it is the only way to distribute energy among neutral particles. I'm just guessing this is what the plasma physicists mean when they say "collision dominated".
If photoionoized is distinct from this, then I think it will be in non-thermal equilibrium, i.e. ions are colder than the electrons.

Theses two cases (thermal EQ and non thermal EQ) actually define two classes of plasmas known as thermal and nonthermal plasmas.
 
  • #6
jasonRF
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I did my graduate work in plasma physics, but do not know anything about astrophysical plasmas. I skimmed the paper because it looked interesting, but you should know that every field has their own jargon, and the jargon in this paper is dramatically different than that used in the ionospheric/magnetospheric physics community I was in. My 'guess' as to what those terms meant was incorrect.

On page 3 of the paper - in the paragraph before section 3 - the authors basically tell you what they mean by some of those terms. They are referring to the primary ionization mechanism. The term 'collision-dominated' has nothing at all to do with thermal equilibrium. Indeed, a collisionless plasmas (such as in the Earth's magnetosphere) can be in thermal equilibrium, although for me the most interesting physics is non-equilibrium.
jason
 
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