Valued Friend, you wrote: “The key issue seems to be the validity of macroscopic MHD.”
Sadly, your correct conclusion has been drawn by Witalis forty years ago in Sweden, when the U.S. decided to stop funding the fascinating Theta-Pinch research even if they were world leaders (just as they did in the Eighties with the Tandem Mirror). Witalis has proven that conventional MHD is an unacceptable oversimplfication when describing Theta-Pinch physics. Remarkably, he noted also that the same conclusion applies to all plasmas with largelarge particle density gradients, like the external regions of a tokamak.
The simple generalization of convenitonal MHD, namely Hall-MHD (or ‘extended MHD’) is much less investigated. However, experiments of Stenzel et al. have shown that Hall-MHD plasmas exhibit filamentation. Many models of filamentation in plasmas are available, from Haines’ model at Imperial College, UK, which relies on electrical conductivity to the Ferro-Fontàn’s model in Argentina which relies on baroclynic term in the in vorticity equation. At UCLA, experiments of Gekelmann et al. have shown that interactions of Alfvèn waves lead also to filamentation. In Italy, transition of a turbulent, MHD plasma to a single, giant filament (Single Helicity state) is observed on the reversed field pinch at Padua (the town of Giotto, the medieval painter who painted the first comet on the history of art)
“cosmology”
Historically, cosmologists study no plasma physics, and plasma physics study no cosmology. (Things are somewhat better for astrophysicists: see e.g. the history of the so-called ‘magnetorotational instability’, which rules turbulent transport of angular momentum in accretion disks. Usually, however, in-depth knowledge of plasmas is reserved to solar physicists and planetologists). However, the original version of the so-called ‘plasma cosmology’ did not take into account any dark matter, as the latter was unknown at the time.
By definition, dark matter has no electromagnetic interaction – i.e., you can see it with the help of electromagnetic radiation at no wavelength. All the same, there is growing consensus on the fact that even dark matter exhibits filamentary structure.
Then, filamentation is really an universal phenomenon (not to mention biological structures). In my opinion, this is why the Dense Plasma Focus is so fascinating from a purely scientific point of view: because it is a cheap factory of the same structures which crowd the Universe.
.
.