Originally Posted by Michael Mozina
See Mozina's post for the full extent of his quote from Alfven. The assumption apparently made by Alfven, that most astrophysical plasmas do not conform to the conditions required for the frozen-field approximation, is now known to be wrong. Before I go on, remember this, from 11 February 2009:
Originally Posted by Tim Thompson
One must fully comprehend that Mozina's blind reliance on Alfven, to the exclusion of everything done in science since Alfven was active, is purely religious and has nothing at all to do with science. That kind of blind faith in any authoritative figure in science must always be rejected, no matter what the science, and no matter the qualifications of the authoritative figure. Science succeeds or fails on its own internal strengths & weaknesses, not on the declarations of authority, despite Mozina's obvious belief that authoritative imprimatur is all that science requires. Why bother with observations? Why bother with controlled laboratory experiments? What use could they possibly be, when the authority of Alfven settles everything?
It is critical to realize that astrophysical plasmas were not well explored when Alfven was active, so there was precious little factual information on which to build a science. Alfven relied mostly on his own intuition, which failed him in this case because it was built on engineering & laboratory experience that did not properly replicate the physical conditions of space & astrophysical plasma. But we must also realize that Mozina fails not only to understand plasma physics, he does not really understand Alfven either. Look again at what Alfven said: "One of the requirements for using the `frozen-in' field concept is that E|| = 0. In order to satisfy this, the electric conductivity parallel to the magnetic field, ||, must be infinite.
" In order for a magnetic field to be literally frozen
into the plasma, the conductivity has to be literally infinite, which will never happen in any physical reality, so it is a trivial observation that no magnetic field can ever be literally frozen into any physically real plasma, and literally everybody in plasma physics knows that very well.
But what else does Alfven say? He says this: "we find that under cosmic conditions, || is usually so large that we can regard it as infinite.
" And what does that mean in any practical sense? It simply means that the mobility of the magnetic field lines relative to the plasma depends on the conductivity. The higher the conductivity, the slower the diffusion of the magnetic field through the plasma, and the more "practically frozen" (not of course literally frozen) it will appear to be. Now, if you are interested in physics that happens in the plasma on a time scale short compared to the diffusion time scale (set by the conductivity), then you can treat the magnetic field for that application as being "frozen". On the other hand, if you are interested in physics that happens on time scales that are long compared to the diffusion time scale of the magnetic field in the plasma, then you cannot use the "frozen" approximation at all, and must be mindful of the mobility of the magnetic field in that application. This in fact is exactly how the frozen field approximation is used in astrophysical plasma physics, and it is in fact precisely in keeping with the rules laid down by Alfven. His mistake was in his assessment of the physical characteristics of the plasma, for which he had not enough factual information at hand. But his assessment that magnetic fields are never really frozen into a plasma was correct, and modern plasma physics adheres to that assessment.
Now, with that said, allow me to repeat myself from 12 March 2009
Originally Posted by Tim Thompson
My quotes from over a year ago show that we are accomplishing nothing in this thread. Mozina continues to make the same tired claims, and we continue to provide the same refutations. The claims and the refutations might be cloaked in slightly different language, but the substance of both remains unchanged. Mozina himself is beyond hopeless, far too deeply engaged in his own private world of ignorance & stupidity. All we can do is repeat & repeat & repeat until one side or the other just gives up from sheer boredom. Such is our fate.
Finally, let me finish with an interesting relevant paragraph:
"The remarkable freezing of magnetic field lines into a plasma can be traced to the large induction L of a typical large scale astrophysical plasma and a correspondingly small resistance R. In electrical circuits the timescale for decay of currents is L/R and, correspondingly, the time scale during which flux freezing holds is L/R and in astrophysics is generally very large."
Plasma Physics for Astrophysics, Russell M. Kulsrud, Princeton University Press 2005, page 2.