I will keep reading these actual articles and posting relevant details.
Kusenko cites a very nice review article from Widrow, 2002:
http://arxiv.org/abs/astro-ph/0207240
widrow said:
Magnetohydrodynamics (MHD) and plasma physics describe the interaction between electromagnetic fields and conducting fluids (see, for example, Jackson 1975; Moffatt 1978; Parker 1979; Freidberg 1987; Sturrock 1994). MHD is an approximation that holds when charge separation effects are negligible. Matter is described as a single conducting fluid characterized by a density field ρ(x, t), velocity field V(x, t), pressure p(x, t), and current density J(x, t). The simple form of Ohm’s law is valid while the displacement current in Amp`ere’s Law is ignored. In Gaussian units, the relevant Maxwell equations take the form ...
Funny, then, that Mozina always wants to talk about MHD
and invent lots of charge separation.
Look, the current density is right in there. Nobody's ignoring it. Widrow continues following Maxwell's Equations and gets to a consequence, a simple fact about astrophysical plasmas:
the flux through any loop moving with the fluid is constant (see, for example, Jackson 1975; Moffatt 1978; Parker 1979), i.e., magnetic field lines are frozen into the fluid
And that's why you'll not see the word "current" in most space plasma papers. Maxwell's Equations give you such a simple relationship between the currents and the fields, that
if you treat the magnetic field as frozen-in, you're automatically treating the source currents correctly. (In the stated approximation---MHD and high conductivity.)
The paper goes on through the observational data, then into models. A historical aside
Soon after the discovery of galactic magnetic fields, Hoyle (1958) began to contemplate their origin. An astrophysical battery seemed an implausible explanation for galactic fields since the voltage required to drive the requisite currents, V ∼ 3 × 1013 Volts, is so enormous. Instead, Hoyle considered a scenario in which magnetic fields are present ab initio in the material that collapses to form a galaxy. Piddington (1964, 1972) championed the primordial field hypothesis and developed models for the structure and evolution of an initially homogeneous field (presumed to be of primordial origin) in a rotating disk galaxy. The primordial field hypothesis hypothesis has been studied recently by Howard & Kulsrud (1997).
So much for the electric universe. The numbers are absurd. Even Fred Hoyle (a proud contrarian, who cannot be accused of being blinded by the mainstream paradigm) could see that. There's not enough EU current to even make the piddly ultra-weak intergalactic fields that are actually there---much less to make the blahtrillion-times-stronger field that EU would need to be there in order to move matter around.
Remember, of course, this is coming from the pen of someone who just (and I quoted him) went through Maxwell's Equations, including current densities of course, in order to find the properties of these plasmas and fields. In figure 9 he shows the current explicitly. On page 44 he brings current densities back explicitly---a few calculations take us outside of the MHD approximation. The first involves diffusive charge separation (like that encountered behind the Moon).
These fields, though weak, are sufficient to explain present-day galactic fields, provided an efficient dynamo develops to amplify them. ... the solar-neighborhood value ζ ≃ 29 km s−1 kpc−1 yields a seed magnetic field B ≃ 10−19 G.
10^-19 gauss! That's an amusingly small number.
To my surprise, electrostatic fields come in:
The Biermann effect can be illustrated by the following simple example. (For a similar pedagogical discussion of the Biermann effect in stars, see see Kemp (1982)). ... An electrostatic force of this type exists in stars (Rosseland 1924) but is extremely small and inconsequential to understanding stellar structure.
Yet another inconsequentially-small force, derived from Maxwell's Equations and the known laws of plasma physics, and derived by people who are
manifestly not ignoring currents. Here's another one:
Lazarian (1992) considered a variant of the Biermann battery in which electron diffusion plays the key role in estab- lishing electric currents and hence magnetic fields. This effect relies on the observation that the ISM is nonuniform, multiphase, and clumpy. Diffusion of electrons from high to low density regions results in an electric field ...
Lazarian (1992) estimated that magnetic fields as high as 3 × 10−17 G can be generated on large scales in the ISM.
3x10^-17 gauss. Again, that's beyond negligible in terms of actual magnetic forces on anything. (Remember that the author's interest in these micro-micro-micro fields is that they can seed a dynamo, and a dynamo can use convection power to make interestingly-strong fields.)
And another:
Gnedin, Ferrara, & Zweibel (2000) performed numerical simulations detailing this mechanism. These simulations followed the reionization of the Universe by stars in protogalaxies. Ionization fronts formed in high density protogalaxies propagate through the Universe. As they cross filamentary structures in the so-called cosmic web, they drive currents which in turn give rise to magnetic fields. The fields produced are highly ordered on a megaparsec scale and have a strength of 10−19 G
Filamentary structures! Currents stretching between protogalaxies! MM surely thinks that someone who knows about such things (i.e. not "ignoring currents") will usher in the Glorious Age When Perratt Shall Be King. Nope, Gnedin et al---using much, much better simulations then Perratt did, and moreover passing peer-review in ApJ---found yet another ultra-ultra-tiny field.
After much discussion of these "late universe" fields sources, Widrow gets around to early-universe sources.
The very first magnetic fields may have been created during an early universe phase transition. These events typically involve fundamental changes in the nature of particles and fields as well as a significant release of free energy
over a relatively short period of time, two conditions that lead naturally to electric currents and hence magnetic fields. Often, the question is not whether magnetic fields are created during an early universe phase transition, but whether these fields are appropriate seeds for galactic dynamos.
And then he goes on to discuss primordial magnetic fields. Of course these are related to currents
Magnetic fields due to a charged scalar field were considered by Calzetta, Kandus, & Mazzitelli (1998) and Kandus et al. (2000). These authors found that charged domains form during inflation which give rise to currents and hence magnetic fields during the post-inflation era.
but as has already been explained, once you have a magnetic field, Maxwell's Equations explain how to carry it forward in time without explicitly solving for these currents. I needn't point out that the author voices no objection to inflation, Higgs fields, dark matter, hypothetical particles, etc..
On the whole, a good review article and yet another patented Mozargument.
a) Mozina quotes a popular-press article as though it supports him.
b) The actual article doesn't support him at all.
c) The article and the references therein, in fact, explicitly contradict pretty much everything Mozina has ever said.
).
yes.
But sadly not for Mr. Mozina. 