Re: Plasma

["John S. Denker" <jsd@AV8N.COM>]

On 11/25/2003 08:50 PM, Ludwik Kowalski wrote:
> They would stay ionized if the responsible agent
> was constantly present, for example, very strong
> flux of cosmic rays. It would be like in a population
> inversion in a laser.

OK, that describes a very hot plasma.  That
is known to exist in some places out there.

A population inversion means it is so stirred
up it can't be described by a temperature at all.
That, too, has been observed.  Indeed a full-blown
natural laser has been observed:
  http://www.google.com/search?q=natural-laser

Meanwhile, there is also a whole lot of plasma
out there that is not very hot.  Yet it is ionized
too.  That was the point of my previous note.
This can be readily understood in terms of the
Saha equation (and the ideas behind it) but
not otherwise AFAIK.

To repeat
 -- the star itself is hot, super-dense plasma
 -- around the star is hot, sparse plasma
 -- the interstellar medium is much cooler
    and even sparser.

For example:  real data:  the solar wind near
the earth is mostly ionized and has a temperature
on the order of 7000 K, if the MIT guys are to
be believed.
http://web.mit.edu/afs/athena.mit.edu/org/s/space/www/helio.review/axford.suess.html

Homework question: convert that temperature to
energy units (eV).  How does that compare to the
ionization energy of hydrogen?