Can two-component plasma fluids (electronic+ionic) be ever treated as a self-gravitating system in any of the real astronomical situations? Please note that a mean-fluid (MHD or EHD) approach is not adopted. It is quite in the absence of massive dust particulates, which are in conventional form, treated as the sources of self-gravity.
Of course they will be, if something has mass, it creates a gravitational field. However, the field strength of the electromagnetic force is several orders of magnitude higher than the force of the gravitational field. Therefore, the mass of the plasma has to be huge in order to hold together but basically stars are nothing else but a big plasma confined by gravitational force.
I want to draw your attention into the Navier-Stokes equation (ion-momentum equation) governing the force balance in the ionic fluid dynamics in the considered system. It is not hard to see that the self-gravitating term in the ion-momentum equation (with respect to the other terms) is negligible. It is, however, not negligible in the case of massive dust grains. I was curious to see why you have failed to see this interested point. Could provide supporting estimations and references in support of your answer?
yes, as the ions have more mass than the electrons, their gravitational force will be stronger and as dust grains are much more massive (and not per se charged - so, there is no electric field to compensate the gravitational force between an uncharged dust grain and and ion/electron) than the ions their gravitational force will be even stronger.
what do you mean, I have failed to see this, I was answering your question, if you have specific interests for, let's say, Navier-Stokes, you should ask about Navier-Stokes. I also don't know what supporting estimations/references you want for my answer, that is basic physics - you can find this in any physics textbook.
Yes, it can. The most interesting model for me is self-gravitating magnetic field, where masses of electrons and ions are neglected, while all inertia and gravitation are due to magnetic field. The frozen-in laws are respected by general relativity. The geometry may be like a z-pinch.
Interesting! Could you please provide some references or links in this regard?
Dear Vladimir Yankov, do you refer to "geometrodynamics", i.e. the investigation of regions of space-time free of matter where Einstein's equations of general relativity are solved assuming that their source term, namely the stress-energy tensor, is only due to electromagnetic fields in free space? As far as I knoww, it is an oldo topic, investigated by Wheeler back in the Sixties. See e.g. J.A. Wheeler, Geometrodynamica (Academic Press, New York 1962).
Dear Andrea,
Yes, I mean "geometrodynamics". Thank you for your reference. I think you saw the filaments near Sgt A published several days ago https://www.newsweek.com/milky-way-new-telescope-captures-clearest-view-yet-our-galaxys-fiery-center-1025555 In my view the filaments are likely lines of magnetic field visualized by "pointed" sources of plasma. But it is near massive black hole, so who knows, may be gravitation play a role too.
Dear Vladimir, thank you very much for Newsweek's article! If you are interested in plasma filaments, then you may enjoy this old paper of mine Eur. Phys. J. D 54, 451–461 (2009)
Thank you, Andrea!
Very interesting paper! I was active in z-pinches in 1978-1985 so it was my please to see modern development.
Dear Vladimir,
you may find more about the same topic at Eur. Phys. J. D 56, 205–208 (2010)
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