Something new under the sun

[Reality Check]

Thank God! finally, you have admitted defeat

Guess what - you have not "won" yet. Reality Check is still here and you have to yet answer the question that you acknowledge that you have to answer:

plasma scalablity and its application to the cosmos

 

[Zeuzzz]

You have 2 further tasks to do to answer the question:

1. How does this scale up to anything larger that a solar system?
2. What is its application to the cosmos?

What do you mean? you want a mathematical relationship? or you want me to copy and paste the part of my last post that looks at a couple of examples of direct plasma scalability over many orders of magnitude?

 

[Dancing David]

The questions does involve orders of magnitude, yes. And remember i am open to plasma cosmology.

However you haven't demonsrated the scales that would be needed for the transformations, i will read the post more carefully tomorrow, but the same annoying questions apply. What would be the scale of conversion and what evidence is there to support it.

Again, I am not trying to lamblast any one I will ask questions that should have answers. i will look through your post and see where you demonsrate the scales of transformation, such as , if there is a plasmoid that acts like a galaxy, what is the scale of the plasmoid to a galaxy? What currents should be visible in the galactic arms through the magnetic fields involved or whatever carrier of the force there is.

If a plasmoid is accountable for th galactic shape then the same force should apply and be scaled appropriately, although it may not be directly related to the scale.

So is there an explanation of how the plasmoid looks like a galaxy or just that it does? Because the reasons the plasmoid are shaped the way that it is will be crucial to the scaling and then the potential observation of what is scaled up to a galaxy.

So if x current flow or magnetic field is needed to create the shape in the lab, what will be the scaled up energy or force needed to do it in a galaxy.

Gravity can model galaxies reasonably, with a kludge. So the scaling should get a kludge as well, but if the scaling says that x-prime should be so large, there should be some figure that could be observed. Which is what i will be asking about.

And also that is where BAC has failed rather well.

 

[Dancing David]

What do you mean? you want a mathematical relationship? or you want me to copy and paste the part of my last post that looks at a couple of examples of direct plasma scalability over many orders of magnitude?

Dude you said that it is scalable! Numbers and explanations would be very nice and would be a demonstration of what might be alleged to be a real theory as opposed to staring at the clouds and seeing pictures.

You said that it can be scaled, so what scale are you using and how do you adjust it from the lab to a galaxy?

 

[Dancing David]

.

RealityCheck, your level of pseudoskeptisism is quite unbelieveable. Did you read Peratts paper? i suggest you start with the equations in section III, and IV. Get back to me when you have come up with why this is all wrong, i would very much like to hear it.

Can you explain the scaling to a galaxy, it is a very relevant question. i have read tha papaer and do not understand it, which is why i ask BAC, what is the force that moves the stars in a flat rortaion curve, it would appear to be magnetism. If so what size does the magnetic field have to be/
Does the internal magneto have to have the same mass as the galaxy or how does it move all the mass of the galaxy?

i am asking these questions because I do not understand how you scale Perrat's model to a glaxy, and BAC has refused to answer my questions.

Do you understand the model well enough to discuss the scaling? What is it that moves the mass is a flat rotations curve? Can it be measured?

 

[Zeuzzz]

The scaling of plasma physics on cosmical and laboratory scales generally involves estimates of the diffusion in plasma, inertia forces acting on the currents, the Coriolis force, the gravitational force, the centrifugal force, and the jxB electromagnetic force [Bostick 1958, Lehnert 1959] .

Specification of plasma density, geometry, temperature, magnetic field strength, acceleration field, and dimension set the initial conditions for simulation . The parameters that delineate the physical characteristics of a current-carrying plasma are the electron drift velocity;

[latex]\beta_{z}=\frac{v_{z}}{c}[/latex]

The plasma thermal velocity;

[latex]\beta_{th}=\frac{v_{th}}{c}=\frac{(\lambda_{D}/\Delta)(w_{p}\delta{t})}{c\delta{t}/\Delta}[/latex]

And the thermal/magnetic pressure ratio;

[latex]\beta_{p}=\frac{n_{e}kT_{e}+n_{i}kT_{i}}{B^2/2\mu_{0}}=\frac{[(\lambda_{D}/\Delta)(w_{p}/\delta{t})]^24(1+T_{i}/T_{e})}{(c\delta{t}/\Delta)^2(w_{c0}/w_{p})^2}[/latex]

Where n is the plasma density, T is the plasma temperature, k is Boltzmann's constant, and the subscripts e and i denote electron and ion species, respectively. The parameter [latex]\delta{t}[/latex] is the simulation time step, [latex]\Delta[/latex] is the cell size, and c is the speed of light. All dimensions are normalized to [latex]\Delta[/latex] and all times are normalized to [latex]\delta{t}[/latex].

The simulation spatial and temporal dimensions can be changed via the transformation;

[latex]{c\delta{t}}{\lambda}=\frac{c\delta{t}\acute{}}{\Delta\acute{}}=1[/latex]

where [latex]\Delta\acute{}=\alpha\lambda[/latex] and [latex]\delta{t}\acute{}=\alpha\delta{t}[/latex], for the size/time multiplication factor [latex]\alpha[/latex]. The values of n, T, B, and E remain the same regardless of whether the simulations are scaled to [latex]\Delta[/latex] and [latex]\delta{t}[/latex] or to [latex]\Delta\acute{}[/latex] and [latex]\delta{t}\acute{}[/latex]. One immediate consequence of the rescaling is that, while the dimensionless simulation parameters remain untouched, the resolution is reduced, that is;

[latex]\omega\delta{t}=\omega\acute{}\delta{t}\acute{}[/latex]

Where [latex]\omega\acute{}=\omega/\alpha[/latex] rad/s is the highest frequency resolvable.

To convert simulation results to dimensional form, it is sufficient to fix the value of one
physical quantity (e.g.,[latex]\beta_{\phi}[/latex])

EDIT: What is up with latex editor on this forum? it works out fine on the usual forum i use I'll copy a pic instead. 1 min.

 

[Zeuzzz]

hope thas a bit clearer than the last one

 

[BeAChooser]

We call the small value the "minimum". We call the big value the "maximum".

Would that be a 2-sigma "minimum" or something else?

The actual value of the thing being measured can be any value between the minimum value and the maximum value but is likely to be close to the measured value.

So the "actual value of the thing" is not necessarily 3.7 million solar masses like you said. I see.

The measured value is 3.7 million solar masses so that is what the actual value will be close to.

But there still is a finite probability that the actual value is close to 40,000 suns. Right?

And by the way ... they didn't "measure" the mass. They inferred it from "measuring" something other than mass.

a zero-sized volume has a radius of zero but we can never measure the radius as zero, only to within a Planck length.

So you are claiming that 10^-35 meters is the same as zero meters? Wouldn't that rule out string theory? Or you suggesting that the billion solar masses collapses until it is just quantum foam? What holds it together then, so that it stays a black hole?

 

[Reality Check]

What do you mean? you want a mathematical relationship? or you want me to copy and paste the part of my last post that looks at a couple of examples of direct plasma scalability over many orders of magnitude?

Peratt is sort of right but also totally wrong. If you were considering just plasma physics you can scale a plasma up to any size that you like. But as Peratt states

The scaling of plasma physics on cosmological and laboratory scales general involves estimates of the diffusion in plasma, inertia forces acting on the currents, the Coriolis force, the gravitational force, the centrifugal force and the j x B electromagnetic force.

He then goes on to ignore everything except the electromagnetic force.

So yes I need the mathematical relationship, including the effect of gravity, the Coriolis force and the centrifugal force.

Also lets have a closer look at the paper which was first published in 1986. This very influential paper must of course have many citations, e.g. a modest 10 a year would give 210 (ignoring 2008). How many do we find - a grand total of 4. So let us look at the citations. Two are from him so they do not count. One is on z-pinches and the abstract does not mention cosmology (it has 96 citations since 2000). The other is on "renewal-at-π cosmology" which seems to present an alternative to all cosmologies (incliding plasma cosmology).

 

[BeAChooser]

Well, gosh BAC here is a sample of what a search for homo polar motor in psts by BeAChooser gives, 11 posts, some are duplicates, and nowhere do youe xplain a model of how the homopolar motor applies to a galaxy.

You once again demonstrate your unwillingness to actually explore the links that have been provided to you in these discussions. Those links have referenced numerous sources ... including peer reviewed scientific papers ... on unipolar inductor (homopolar) models for various space objects, including galaxies. Some sources were even written by a Nobel Prize winner in physics. You've also shown no willingness to do any internet browsing on your own. You apparently want to be spoon fed.

Browse under the right keywords and you'll get plenty of hits on the subject. This one, for example,

http://www.plasma-universe.com/index.php/Homopolar_generator

contains numerous references. Here are other examples of the type of sources that are easily found discussing this topic:

http://arxiv.org/pdf/astro-ph/0606489

http://adsabs.harvard.edu/full/1978Ap&SS..54..279A

So if you really want to understand the proposed model, you need only try. Your apparent unwillingness to do that is why I've decide it's a waste of time to respond to most of your posts, David.

 

[BeAChooser]

Plasma physics predicts Birkeland currents. plasmiods, double-layers and all of the other predictions that you attribute to "plasma cosmology".

You're hand waving, RC. Plasma physicists do indeed predict all the above types of phenomena. For good reason. Yet, mainstream astrophysicists don't seem to even have those terms in their lexicon. Why is that?

One more time - a simulation is not the thing being simulated.

You mean like that large computer model you touted that uses warm dark matter to create a filamentary universe?

And speaking of experiments ... how about this one from the Big Bang community:

http://www.telegraph.co.uk/earth/ma...&grid=&xml=/earth/2007/12/23/scicosmos123.xml "'Test tube universe' hints at unifying theory, By Roger Highfield, Science Editor ... snip ... 26/12/2007, A "universe in a test tube" that could be used to assess theories of everything has been created by physicists. ... snip ... What is remarkable is that atoms in the liquid, at temperatures within a thousandth of a degree of absolute zero, form structures that, according to the team at Lancaster University, are similar those seen in the cosmos."

I think mainstream astrophysics and cosmology just get sillier and sillier in what they propose as "evidence" to support their gnome filled theory.

 

[Reality Check]

You're hand waving, RC. Plasma physicists do indeed predict all the above types of phenomena. For good reason. Yet, mainstream astrophysicists don't seem to even have those terms in their lexicon. Why is that?

Give me a list of the mainstream astrophysicists that know nothing about plasma physics. I will bet that it is small. They accept that plasma physics is important for plasmas of any size. The effect of plasma physics outside of plasmas is small. Look up plasma in Wikipedia

You're
You mean like that large computer model you touted that uses warm dark matter to create a filamentary universe?

You mean the large computer model that includes every known factor to simulate the universe of which warm dark matter is just one?

And speaking of experiments ... how about this one from the Big Bang community:

http://www.telegraph.co.uk/earth/ma...&grid=&xml=/earth/2007/12/23/scicosmos123.xml "'Test tube universe' hints at unifying theory, By Roger Highfield, Science Editor ... snip ... 26/12/2007, A "universe in a test tube" that could be used to assess theories of everything has been created by physicists. ... snip ... What is remarkable is that atoms in the liquid, at temperatures within a thousandth of a degree of absolute zero, form structures that, according to the team at Lancaster University, are similar those seen in the cosmos."

I think mainstream astrophysics and cosmology just get sillier and sillier in what they propose as "evidence" to support their gnome filled theory.

That is not evidence, it is a press release including the usual hype. The scientists state that the structures are "similar" to those seen in the cosmos.

 

[Reality Check]

Would that be a 2-sigma "minimum" or something else?

It is not stated in the article so we cannot tell. Why don't you contact the authors if it is so important to you?

So the "actual value of the thing" is not necessarily 3.7 million solar masses like you said. I see.

You do not see. It is very likely to be 3.7 million solar masses since that is what the scientists state. Scientists tend to state the most likely values of measurements or calculations.

But there still is a finite probability that the actual value is close to 40,000 suns. Right?

Yes.

And by the way ... they didn't "measure" the mass. They inferred it from "measuring" something other than mass.

No they did not "infer" the mass. They calculated the mass using the orbits of stars around the black hole.

So you are claiming that 10^-35 meters is the same as zero meters? Wouldn't that rule out string theory? Or you suggesting that the billion solar masses collapses until it is just quantum foam? What holds it together then, so that it stays a black hole?

[/quote]
No I am not. Its mass keeps it as a black hole.

 

[Reality Check]

You seem completely incapable of actually reading any of the material i post. Please look at some of the work in my last post.
Hannes Alfven was one of the original advocates of a plasma cosmology approach, and so you saying that all his amazingly accurate predictions do not validate the very model he was advocating is utterly ridiculous.

I did read that paper. You apparently think that the title of the paper, "Alfven's programme in solar system physics" contains the word cosmology.

It is extremely comparable. The sun is made of highly conducting plasma, just as with the Terrella.

So what?

But they are govened by the same laws due to plasma scalability, the whole point of the post (incase you hadn't noticed) Maybe you should read some of the papers i supplied? you obviously didn't.

If this is your view, could you please post your refutation of plasma scalability from force free configurations?

So post your support of plasma scalability including forces from the real world - including gravity.

congratulations on not understanding anything being presented here. Of course gravity is not at work in the experiment, EM forces are. And this indicates that galxies, that possess similar rotational properties to the experiments, and many other similarities, are not dominated by gravity pulling everything into a central point, but could be formed by similar EM forces that can account for this spiral shape. This is all without the need of invoking tremendous amounts of hypothetical dark matter or dark energy. A theory which needs no such epicycles as these is the more powerful theory.

So you admit that only EM forces are considered. A partial model is even worse than a wrong model since it wastes peoples time.
Please learn some elementary physics or better English. Galaxies are not "dominated by gravity pulling everything into a central point". They rotate and that accounts for the spiral shape. We do not need dark matter to account for the shape of galaxies. Your "epicycle" is the assumption that plasma physics is the dominant force in the universe.

 

[Reality Check]

Zeuzz, while we are in the question of "scalability" and its application to cosmology:
Have you considered gravitation scalability and its application to cosmology?

 

[Klimax]

BAC,How much do you know math. statistic?
If you do,you do not seem to use it...

 

[Dancing David]

You once again demonstrate your unwillingness to actually explore the links that have been provided to you in these discussions. Those links have referenced numerous sources ... including peer reviewed scientific papers ... on unipolar inductor (homopolar) models for various space objects, including galaxies. Some sources were even written by a Nobel Prize winner in physics. You've also shown no willingness to do any internet browsing on your own. You apparently want to be spoon fed.

Browse under the right keywords and you'll get plenty of hits on the subject. This one, for example,

http://www.plasma-universe.com/index.php/Homopolar_generator

contains numerous references. Here are other examples of the type of sources that are easily found discussing this topic:

http://arxiv.org/pdf/astro-ph/0606489

http://adsabs.harvard.edu/full/1978Ap&SS..54..279A

So if you really want to understand the proposed model, you need only try. Your apparent unwillingness to do that is why I've decide it's a waste of time to respond to most of your posts, David.

So, in truth, you are saying "I won't answer the questions."

Why is that BAC?

Why when asked for a direct , short answer you refuse to provide one?

Hmmm?

Again you are using appeals to emtion, instead of answering questions.

I suspect you just don't know what you are talking about.


http://arxiv.org/PS_cache/astro-ph/pdf/0606/0606489v3.pdf

As in that theory, galactic nuclei
are dark objects where gravity prevents the escape of most radiation.
In this case, collapse is counteracted by rising internal pressure and
black hole singularities don’t occur.

Suppose a supermassive body’s gravity exceeds the opposing nuclear forces
and collapse begins. Falling inward, of course its particles gain kinetic energy,
raising its temperature and pressure. Collapse continues as long as the body can
radiate the acquired kinetic energy.
However, the escape of radiation (including neutrinos) is cut off before the
body shrinks to 1 percent of the photon orbit radius. And contraction stops when
its gravity is counterbalanced by increased radiation pressure. Since there is no
collapse of space-time here, the result is a darkened object of finite dimensions.
Extreme gravity is matched by extreme temperatures and pressures, with massive
particles having velocities very close to the local speed of light.
In wave gravity, the trajectory of a massive particle with nearly the speed of
light approximates that of a light ray in a gravitational field [1]. So the above
equations apply approximately to the escape of all relativistic particles from supermassive
bodies. Rather than energy, the critical factor for the escape of relativistic
particles is the direction of their trajectories. With symmetrical gravitational fields,
it’s always possible for some light or matter to escape along trajectories aligned
precisely with the field direction.

Sooooo :

here is one of your alleged explanations except that it isn't yours.

And in the abstract it just asserts that internal pressure will prevent collapse, now at what radius of concentration is this?

Are they violating GR?

or as they say later 'less that tna 1% of an orbiting photon radius", so we are at a very small scale and so you don't have an extended plasmoid but a 'black hole'?

And this paper just seems to assert without evidence that space/time as expressed in GR is incorrect.

Hmm, still no answer, to which question were you prenteding this was an answer?

 

[Dancing David]

You're hand waving, RC. Plasma physicists do indeed predict all the above types of phenomena. For good reason. Yet, mainstream astrophysicists don't seem to even have those terms in their lexicon. Why is that?

Because if they are like you they don't answer a direct questions when asked!

So what keeps a Lerner plasmoid extended in a volume of space BAC? You presnted this theory, so answer the following questions about it:

Say one that is 40,000 soloar masses in an area with a radius of 43 AU,
What size is the alleged plasmoid?
What force keeps it from undergoing gravitational collapse to an object of such gravitational force that it is called a 'black hole'? IE photons will not exit the event horizon.
You have not answered the question.

So far you linked to one paper, it described an object that was very, very small and then just asserted that the photons could escape the gravitational field if they went the right direction. Which is sort of wrong.

So why won't you answer the direct question about the Lerner plasmoid that you allege is at the center of the galaxy?

You can't, you apparently just wave words around and you don't know what they mean.

 

[Dancing David]

BAC,How much do you know math. statistic?
If you do,you do not seem to use it...

Hello, Welcome!

You shall see many things that BAC does , but answer a direct question is not one of them.

 

[Zeuzzz]

Zeuzz, while we are in the question of "scalability" and its application to cosmology:
Have you considered gravitation scalability and its application to cosmology?

[....]

So post your support of plasma scalability including forces from the real world - including gravity.

So you admit that only EM forces are considered. A partial model is even worse than a wrong model since it wastes peoples time.
Please learn some elementary physics or better English.

What the hell are you talking about? are you seriously suggesting that Peratt just forgot to include the force of gravity in his model? I have continually asked to to actually read and try to comprehend his work, but its obviously completely above your head.

I'll have one more go. (both papers can be seen in full in the links supplied above)

Evolution of the plasma universe. I - Double radio galaxies, quasars, and extragalactic jets - Section III and IV contains the relevant relationships and the simulation parameters used in the supcomputer model. As requested I posted above the necissary plasma scaling laws, and i really cant be bothered to post his material in its entirity, so i suggest you actually read what he is saying.

Evolution of the plasma universe. II - The formation of systems of galaxies Looks at how these models can create the shapes of various generation of galaxies, and expands on the EM relationships between plasma's addressed in the previous paper.

r HE evolution of cosmic plasma from a filamentary 1 state to the development of double radio sources and quasars was investigated in the first part to this sequel paper (Paper I) [1]. The time frame of this study, based upon scaling simulation parameters to galactic dimensions, spanned some 108-109 years. In this paper (Paper II), the evolution for the next 1-5 x 109 years under the influence of electromagnetic forces acting on the plasma
is investigated. The importance of electromagnetic forces in galactic and stellar evolution derives from the fact that the universe is largely matter in its plasma state. The observed stars are composed of plasmas, as are the interstellar and interplanetary media and the outer atmospheres of planets.

The neutral Hi regions in galaxies are also plasma although the degree of ionization is probably only 10^-4. Both the intra- and intergalactic media then consist of plasma, leading to the coinage of the term "plasma universe." Electromagnetic forces can then be expected to play a crucial role in the development of the plasma universe including both the formation of systems of galaxies and the formation of stars within the dusty galactic plasmas.

Although the gravitational force is weaker than the electromagnetic force by 39 orders of magnitude, gravitation is one of the dominant forces in astrophysics when electromagnetic forces neutralize each other, as is the case when large bodies form [5]. Indicative of the analogy of forces for the motion of electrons and ions in the electromagnetic field and the motion of large bodies in the gravitational field is the ease with which a plasma model may be changed to a gravitational model. This transformation requires only a change of sign in the (electrostatic) potential calculation such that like particles attract instead of repel, followed by setting the charge-to-mass ratio equal to the square root of the gravitational constant (a gravitational model cannot be simply changed to an electromagnetic model as the full set of Maxwell's equations are required in the latter). [....]

It is the purpose of this paper to continue the investigation of the dynamics of the denser interacting plasmas pinched within the filaments by means of the electromagnetic and gravitational force laws. That this is possible is due largely to the advent of the particle simulation of dynamic systems in three dimensions on large computers, allowing the computation of up to many millions of charge and mass particles according to their respective force laws. This approach to the study of cosmic plasma is labeled "gravito-electrodynamics" [8].

And for some further reading, and an expansion on the EM forces involved in this galaxy model, may I suggest The role of particle beams and electrical currents in the plasma universe (can be seen in full here

3-dimensional particle-in-cell simulations of spiral galaxies - Galactic and intergalactic magnetic fields; Proceedings of the 140th Symposium of IAU

Rotation Velocity and Neutral Hydrogen Distribution Dependency on Magnetic Field Strength in Spiral Galaxies - Astrophysics and Space Science, Volume 227, Issue 1-2, pp. 167-173, 1995


Peratt included standard gravity as a vital variable in his model, and it did have an effect on the shape of the galaxy, although the EM forces in the plasma were shown to dominate the overall morphology.

You are a joke reality check. Every comment you have posted since my previous reply to sols little challenge has been either completely misrepresenting the material presented, or just make arguments on authority. Ever heard of a logical fallacy? If you cant dismiss the message, shoot the messsenger.

If you think this is such a bad scientific model with no merit, then please add your scientific objections to it. For the twentieth time. Hand waving and just saying "this paper only has twenty citations, so therfore it must be wrong" is one of the stupidest reasons to dismiss material I have heard in a long time. There is a good reason why they have not been cited as much as other papers on mainstream scientific subjects, as they contradict the gravity driven Big Bang picture that nearly every scientist in the world has been educated to believe. It seems that many scientists like Peratts work, and many have contributed to this controversial field since his original publications.

I suggest you read some of the articles that have cited peratts work, including some of the recent independant plasma astrophysicists that are expanding on his model. And the two papers I cited above are not the only ones, there are many others if you would care to look at them aswell (i'm not holding my breath). Heres just a couple;

Are rotation curves in NGC 6946 and the Milky Way magnetically supported? Astronomische Nachrichten, Vol.328, Issue 1, p.92-98 (AN Homepage) 01/2007.

The inner disk rotation of NGC 6946 and the Milky Way is dominated by gravity but magnetism is not negligible at radii where the rotation curve becomes flat, and indeed could become dominant at very large radii. Values of the order of 1 μG, or even less, produce a centripetal force when the absolute value of the slope of the curve [B_ǎrphi, R] (azimuthal field strength versus radius) is less than the slope of a B_ǎrphi-profile proportional to R-1. The ∝ R-1-profile is here called the critical profile. From the hypothesis of magnetically driven rotation curves, the following is to be expected: at large radii, a ``subcritical'' profile (slope flatter than R-1); at still larger radii a B_ǎrphi-profile becoming asymptotically critical as the density becomes asymptotically vanishing. Recent observations of magnetic fields in NGC 6946 and the Milky Way are in very good agreement with these predictions.

Magnetic fields and large scale structure in a hot universe. I. General equations. - Astronomy and Astrophysics, v.326, p.13-22

We consider that no mean magnetic field exists during this epoch, but that there is a mean magnetic energy associated with large-scale magnetic inhomogeneities. We study the evolution of these inhomogeneities and their influence on the large scale density structure, by introducing linear perturbations in Maxwell equations, the conservation of momentum-energy equation, and in Einstein field equations. The primordial magnetic field structure is time independent in the linear approximation, only being diluted by the general expansion, so that {vec}(B) R^2^ is conserved in comoving coordinates. Magnetic fields have a strong influence on the formation of large-scale structure. Firstly, relatively low fields are able to generate density structures even if they were inexistent at earlier times. Second, magnetic fields act anisotropically more recently, modifying the evolution of individual density clouds. Magnetic flux tubes have a tendency to concentrate photons in filamentary patterns.

The physics of fast Z pinches - Reviews of Modern Physics, vol. 72, Issue 1, pp. 167-223 - 01/2000

The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. At present Z pinches are the most intense laboratory x-ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizing the present knowledge of physics that governs the behavior of radiating, current-carrying plasma in fast Z pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasiequilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Nonmagnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented.

Magnetism in the spiral galaxy NGC 6946: magnetic arms, depolarization rings, dynamo modes, and helical fields - Astronomy and Astrophysics, Volume 470, Issue 2, August I 2007, pp.539-556

Context: The spiral galaxy NGC 6946 hosts magnetic spiral arms, highly aligned magnetic fields between the gas/optical arms. Aims: The origin of the magnetic phenomena and their relation to the interstellar gas are investigated. Methods: NGC 6946 was observed in total intensity and linear polarization in five radio bands between 3 cm and 21 cm. Maps of spectral index, Faraday rotation and depolarization were derived. Results: At the inner edge of the inner gas spiral arm the ordered magnetic field is only mildly compressed and turns smoothly, to become aligned along the gas arm. Hence the field is not shocked and is probably connected to the warm, diffuse gas. At larger radii, two bright magnetic arms between the optical arms are visible in polarized intensity. The field in the northern magnetic arm is almost totally aligned. - In the gas/optical spiral arms, the total (mostly turbulent) magnetic field is amplified to ≃20 μG. Its energy density is ≃10 times larger than that of the ionized gas and is similar to that of the turbulent gas motions in the inner galaxy. The magnetic energy exceeds that of the turbulent energy in the outer galaxy. All energy densities in NGC 6946 are about one order of magnitude larger than those in the Milky Way. Conclusions: Density waves in the inner gaseous spiral arms mildly compress the field. Dynamo action probably generates the magnetic spiral arms. The magnetic field is dynamically important, interacts with the gas flow and possibly determines the properties of the gas spiral arms.