The paper i have quoted is a following to a previous paper from 1992 and this is why they adress particulary the flaring aspect.

Maybe you can find the paper here. I cannot access the PS file so i can`t verified the contend.
Edouardo Battaner site

http://www.ugr.es/~fteorica/astro/battaner.html

Other paper i find.
Local hydromagnetic simulations of accretion disc turbulence provide now the most convincing evidence that the origin of turbulence in discs could be the Balbus-Hawley magneto-rotational instability. The main results of such calculations are highlighted with particular emphasis on the generation of large scale magnetic fields. Comparison with mean-field dynamo theory is made. This theory is then used to address the question of the launching and collimation of winds emanating from the disc surfaces. (17 September 1999)
http://antares.ncl.ac.uk/~brandenb/papers/rs.ps.gz

The 1992 paper is not on Battaner's website, nor is it anywhere else, except in the pages of Nature. That's probably why, because Nature is usually much less liberal than other publications, about reproducing their papers off site. Until & unless I go to the library and look up the back issues of Nature, that will remain open.

You should pay more attention to the point. That paper does not even talk about galaxies at all. They are talking about accretion disks, such as circumstellar disks or accretion disks around black holes. They are talking about dense plasma and strong magnetic fields, and they don't even mention rotation curves. There is nothing in this paper that addresses any of the issues we were talking about.

If you are going to hunt for papers, then hunt for papers that talk about flat spiral galaxy rotation curves and magnetic fields.

I recognize that. In fact in optically thick nebula we discount recombinations directly into the ground state for the very reason you state, and use instead an effective so-called "Case B" recombination rate coefficient. This effective recombination to all states other than the ground state is about 62% of the TOTAL recombinations at an electron temperature of 10,000K (see Osterbrock's book), and slightly less than that at 20,000K.

The Stromgren Depth dR can be defined from photo-ionization equilibrium:
dR = U(H) * c / (alpha_B * n_e), where U(H) is the ionization parameter and is the ratio of the number density of hydrogen ionizing photons to the number density of protons, c is the speed of light in a vacuum, and alpha_B is this case B recombination coefficient for Hydrogen.

Anyhow, while it is true that recombinations to excited states followed by cascades to lower levels allows for a finite stromgren sphere (as does U), recombinations to the ground state are not insignificant (~40%, as above). But then this may not affect the discussion you are having with Thomas or Orion38.

Cheers.

Here it is but i am not quite sure if is it the same article from Nature you mention.If it is the case why this article publishing by Nature is not valid for you?
You can try find similar abstract for more.

http://adsabs.harvard.edu/cgi-bin/np...52B&db_key=AST

Here we argue that an azimuthal magnetic field can carry slightly ionized gas with the general galactic rotation, rendering dark matter unnecessary. For the illustrative case of M31, a magnetic field of 6 micro-G is required, and the synchrotron emission of relativistic electrons in this field is compatible with the observations.

All observations which unambigously come to the conclusion of the presence of 'Dark Matter' are indeed observations of gas (this is what I read out of the information on Battaner's website http://nedwww.ipac.caltech.edu/level5/March01/Battaner/). There have been observations of stars as well, but (according to Battaner) these have various sources of uncertainties.
I am not an expert in this field, but I reckon that if you dismiss all the gas-observations for the reason pointed out by me, the evidence for Dark Matter would become rather thin.

Do you ever pay attention to anything somebody else says? What you posted is the abstract, not the paper; you can't download the paper from that site. As for not being valid, I never suggested that it was not valid!! Why did you even ask such a question?? I said "Until & unless I go to the library and look up the back issues of Nature, that will remain open.". I can't know if there are rotation curves in the paper until I actually see the paper!! PAY ATTENTION!!!

What about lensing?

I only bad translated what you mean by "The 1992 paper is not on Battaner's website, nor is it anywhere else, except in the pages of Nature. -That's probably why, because Nature is usually much less liberal than other publications, about reproducing their papers off site.-"
So I have interpreted because Nature is the only place the article is avalable it is not serious or not worth the time for publishing it.

Why the article is not avalable from the abstract make me wonder why it is not avalable?Is it because the article really challenge the dark matter?
Like you see this is not because i don`t pay attention but sometimes mislading from bad translation.
Again sorry about that.
:-?

Is there a case where galaxies are suppose to be lensing by "dark matter" outside galactic halos?

Is there ever! In fact, there's an entire LENSING SURVEY that relies on this.

There are strong lensing statistics and weak lensing statistics. Lensing is really a huge thorn in the side for those that argue that mass isn't what's causing the flat rotation curves. There's actually a good comparison between lensing and Keplerian probes of rotation curves. This is, I think, one of the reasons dgruss has said that the most favored explanation is dark matter. I have yet to see someone explain away lensing results without appealing to dark matter, but you're free to look.

Not only that, the famous Hubble Image of a Gravitational Lens shows far more matter than is observed for luminous matter in the cluster.

In the precise case of the Hubble image of Galaxies lensing if I remember show lot of Galaxies close together in a small package.So the possibility than the lensing is caused by gases is more likely the explanation.
What I want to know is if it exist isolated galaxies -so not close together-being lensing?

Actually, this isn't the case at all. The index of refraction for IGM gas is way, way, way too low for a lensing event such as this to be seen.

Absolutely.

A quick adsabs search revealed these salient results. There are hundreds of others:

Chen, Da-Ming 2003, Astrophysical Journal Strong Gravitational Lensing and Galactic Bulges

Hoekstra, H., Franx, M., Kuijken, K., Carlberg, R. G., & Yee, H. K. C. 2003, Monthly Notices of the Royal Astronomical Society Lensing by galaxies in CNOC2 fields

Moustakas, Leonidas A. & Metcalf, R. Benton 2003, Monthly Notices of the Royal Astronomical Society Detecting dark matter substructure spectroscopically in strong gravitational lenses

Turner, C. M., Keeton, C. R., & Kochanek, C. S. 2002, American Astronomical Society Meeting The Angular Structure of Four-Image Gravitational Lenses

Metcalf, R. B. 2002, American Astronomical Society Meeting Gravitational Lensing by Galactic Substructure and the Nature of Dark Matter

Möller, Ole, Natarajan, Priyamvada, Kneib, Jean-Paul, & Blain, A. W. 2002, Astrophysical Journal Probing the Mass Distribution in Groups of Galaxies using Gravitational Lensing

Winn, J. 2002, American Astronomical Society Meeting Gravitational lenses, cosmology, and galaxy structure

Oguri, Masamune, Taruya, Atsushi, Suto, Yasushi, & Turner, Edwin L. 2002, Astrophysical Journal Strong Gravitational Lensing Time Delay Statistics and the Density Profile of Dark Halos

Chiba, Masashi 2002, Astrophysical Journal Probing Dark Matter Substructure in Lens Galaxies

Fox, David C. & Pen, Ue-Li 2001, Astrophysical Journal Gravitational Lensing by Galaxy Groups in the Hubble Deep Field

Agree.The effect looks more like galaxy galaxy lensing. Why this is presented like a case for dark matter lensing?What is the difference in that case?

Agree.The effect looks more like galaxy galaxy lensing. Why this is presented like a case for dark matter lensing?What is the difference in that case?[/quote]

Because the mass of the lens can be determined from gravitational lensing. This means that we can get a mass to light ratio which is shown to be consistent with the mass to light ratio one gets assuming dark matter models.

[quote="Tim Thompson"]The real explanation as stated by Alfven
Dynamic Electromagnetic Forces in Cosmic Plasmas
  Plasmas respond to the electrical physical laws codified by James Clerk Maxwell and Oliver Heaviside in the late 1800's.  An additional single law due to Hendrick Lorentz explains the "mysterious" stellar velocities described above.
d/dt(mv) = q(E + v x B)

Simply stated, this law says that a moving charged particle's momentum (direction) can be changed by application of either an electric field, E, or a magnetic field, B, or both.  Consider the mass and charge of a proton for example.  The electrostatic force between two protons is 36 orders of magnitude greater than the gravitational force (given by Newton's equation



The simple application of the Lorentz force equation ("crossing" the direction, v, of the current into the direction, B, of the magnetic field) yields a rotational force.  Not only does this effect explain the "mysterious" tangential velocities of the outer stars in galaxies, but also (in scaled down version) the observed fact that our Sun rotates faster at its equator than at higher (solar) latitudes.

Orion, this is the biggest bunch of bologna I've seen in a long time. The fact is the halo of the galaxy is spherically symmetric and the orbits of things that are above the pole are just as zippy as things near the disk. Thus your argument falls flat on its face.

Wrong, the major difference betwen dark matter and normal matter lies in the fact that dark matter is inclassifiable as to know of what it is composed.

Now another subject of interest we have discuted about MHD and Alfven theorem i find this explanation from Plasma Cosmologist
Quote:
Another problem is the concept of magnetohydrodynamics, or MHD. This concept was developed by Alfven in the 1930s. It postulates that plasmas have the potential to trap and carry magnetic fields, a concept called the "frozen-in flux theorem." However, Alfven later dismissed MHD as a bad concept, saying that it "makes you think you understand a phenomena when you have grossly misunderstood it." Unfortunately, MHD was mathematically elegant and rigourous, approximating plasmas as superconducting gases (such superconduction cannot allow electric fields to form) and likewise treats them via fluid dynamics (Navier-Stokes systems)--hence the "hydro" part of "magnetohydrodynamics"--so the deductive thinkers of mainstream cosmology adopted the frozen-in field concept. Alfven spent most of his life trying to convince the scientific community of the flaws of MHD. "It is only the plasma that does not 'understand' how beautiful the theories are and absolutely refuses to obey them," he said in his Nobel Prize speech. He was right--plasmas are mathematically anarchic for one thing. Also, there is an effective resistor preventing superconductivity--the magnetic fields themselves. Furthermore, Alfven applied MHD only to extremely dense plasmas, something which is well outside our experience here on Earth and has yet to be observed in space. Even simple visual observation will tell you that MHD cannot be applied to astrophysical plasmas. EM radiation emitted by numerous sources cannot come to be without electric fields and currents. However, we still have MHD employed by mainstream astrophysicists, now over six years after Alfven has passed away. They continue to apply it to all plasmas, laboratory and astrophysical. They have even forgotten that it was his concept to begin with, with one particularly rude comment saying "He is not Saint Alfven." Eric Lerner points this fact out, saying "The fact that the MHD model itself is Alfvén's was gradually obscured as physicists came to rely on new textbooks by astrophysicists like Lyman Spitzer and S. Chandrasekhar."

You really think you can just push a star around with a magnetic field like that? It's obviously ridiculous. However, let's make "obvious" a quantified observation. I will assume a velocity ~200 km/sec and a distance of 20 kpc (look like reasonable numbers to me, feel free to substitute your own and see what happens). Assuming circular motion, then the acceleration a = (v^2)/r and we get a = 6.485 x 10^-11 m/sec^2. For 1 solar mass (1.989 x 10^30 kg) the force ma = 1.29x10^20 N ("Newtons").

Now that force has to equal q(VxB), where "q" is the net charge on the star, and VxB is the vector cross product of the velocity & magnetic field. I will assume an angle of 90 degrees, so that sin(theta) is 1 and the force applied by the B field is maximized. If V is about 200 km/sec, and B is 10^-10 Tesla (1 Gauss = 10^-4 T, so 10^-6 G = 10^-10 T), then the magnitude of VxB is just the product or 2X10^5 m/sec x 10^-10 T = 2x10^-5. So the charge "q" in Coulombs should be 1.29x10^20/2x10^-5 = 2.58 x 10^15 (since I am using "mks" units, I may be missing a 4*pi*e0 or some such in here, so E&M whizzes are welcome to correct the heck out of me if I am messing this up; I think I've got the units right).

This tells me that to reproduce the observed stellar motion, a star needs to have an excess charge of magnitude 2.58x10^15 Coulombs, and I have deliberately igonred the sign of the charge for now. There are ~10^57 baryons in a one solar mass star, and 2.58X10^15 C represents 1.61x10^34 electrons. So there are enough neutral atoms going into the solar mass, that such an excess electrostatic charge might be accomodated.

However, we know from the structure of the corona, and the thermodynamics of stars, that a star should have a net positive charge, because electrons are lighter than protons and should favorably escape under thermal equilibrium (see "On the global electrostatic charge of stars", L. Neslusan, Astronomy and Astrophysics 372(3): 913-915, June 2001, and references therein). For the sun, we expect a net charge of roughly +77 C. That's a far cry short of 2.58^10^15 C, and I suspect that even if I made a mistake with the units somewhere, it won't cover that kind of a gap.

So it appears that the electrostatic chrage per star that is required for such a model to work, is far in excess of that which physics allows. And now we should think about the sign. All stars should show a net positive charge, never a net negative charge. I don't know off hand what the direction of the outer galaxy magnetic field lines is, but I do know that the direction of the VxB force depends on that direction, so it had better be right too. And also note that if the force is inward in the outer galaxy, it must be outward in the inner galaxy, and there should be some indication of that force (the B field will be stronger, and in the reverse direction, since it is a dipole, and the stars will see a much smaller enclosed mass within their orbits and therefore a smaller gravitational force).

And finally note that by using 200 km/sec, which is the approximate speed of the star in the galaxy rest frame, I have maximized the effect by assuming a stationary B field. the "V" that goes into the vector product VxB is the velocity of the star relative to the B field, and that's a lot more likely to be smaller than to be larger.

I cannot see a physical justification for this model.

This too has a lot of physical problems. If the solar magnetic field is roughly dipolar, then the relative motion between gas and magnetic field is much the same as the case of the galactic field and stars; the force will be inwards or outwards. But to create differential rotation the force has to be a shear along the surface of the star. We already know that this can be produced by uneven heating of the convective layer from below, due to a non uniform energy flux leaving the core, due to rapid intenral rotation. So it is much easier to explain as a hydrodynamic instability.

Observation of the sun's magnetic field shows that it's overall shape is not that of a classic dipole (it has no polar cusps), and that the field is essentially radial. in that case the VxB force will be directed axially, which could produce a desired shear in a rotating system. However, it will force the protons (and positive ions) & electrons in opposite direction, and that would not produce a bulk shear. So this won't create differential rotation either.

But the magnetic field of the sun at the surface is extremely complex, as is the magnetic field below the photosphere. It is more likely that the differential rotation is a hydrodynamic instability, and that the magnetic field responds to that. But the magnetic field could play a larger role, and I am sure the theoretical question as to which does exactly what remains open. For gory details, consult Theory of Rotating Stars, Jean-Louis Tassoul, Princeton University Press, 1978 (old but still unsurpassed for the basics).

Half-wrong. You overlook the fact that there is not just one kind of "dark matter". The phrase "dark matter" is used, carelessly perhaps, to refer to two distinctly different kinds of "dark" matter.

Galaxy rotation curves and the dynamics of galaxies in clusters clearly indicate either the presence of "dark" matter, or of some as yet unaccounted force (such as in the MOND interpretation). The matter in question could easily be ordinary gas that has as yet escaped detection, or some collection of black holes, neutron stars, white dwarfs, brown dwarfs, planets, or some such. There is nothing "inclassifiable" about such things, and they are perfectly acceptable forms of "dark matter".

The other form of dark matter, the one you are complaining about, is the 'non-baryonic" dark matter. That kind of dark matter is required by analysis of cosmic background radiation anisotropies, if one assumes that an expanding universe cosmology is correct. But you make a significant mistake, that is common of the critics of "dark matter" you said that dark matter was "inclassifiable". That word means that you already know that dark matter will never be classified as anything, because it is an impossible thing to do. The correct word is "unclassified". That word means that it hgas not been classified yet, but will be (or may be), eventually, classified.

Therein lies the extreme illogic of the critics. How do you know that dark matter will never be directly observed? How does anyone know that? And why can't you show me the fundamental physical principle that prevents matter from being dark or non-baryonic?

What physical principle makes than 99% of the matter of the universe being dark?

What`s your opinion about the explanation for MHD given by Plasma Cosmologist- sorry for quoting again -
"Another problem is the concept of magnetohydrodynamics, or MHD. This concept was developed by Alfven in the 1930s.
It postulates that plasmas have the potential to trap and carry magnetic fields, a concept called the "frozen-in flux theorem." However, Alfven later dismissed MHD as a bad concept, saying that it "makes you think you understand a phenomena when you have grossly misunderstood it." Unfortunately, MHD was mathematically elegant and rigourous, approximating plasmas as superconducting gases (such superconduction cannot allow electric fields to form) and likewise treats them via fluid dynamics (Navier-Stokes systems)--hence the "hydro" part of "magnetohydrodynamics"--so the deductive thinkers of mainstream cosmology adopted the frozen-in field concept. Alfven spent most of his life trying to convince the scientific community of the flaws of MHD.

More on my previous post.

This one part of the explanation. All the process explained by Elfven here:

http://www.electric-cosmos.org/galaxies.htm

Well, if it isn's baryonic, then what is it? Such a new class of particles would require a fundamental reshaping of particle physics. As for other, less exotic particles, neutrinos would not stay bound to a galaxy--moving too darn fast. Anything else has too big of a cross section to be a plausible candidate.

[quote="Tim Thompson"]Simple because Battener have used the MHD.So if Battener have used the right equation in this case Boltzman and Maxwell equation this would work.
Try it .

Yes, I intended to deal with that, but ran out of time last night. My opinion is that it is stupid.

" ... approximating plasmas as superconducting gases". False. There is no such approximation in MHD. The resistivity of the plasma is a crucial part of understanding plasma physics. Alfven was wrong to reject MHD, and that's why he sank from fame to relative obscurity. MHD is the only physically correct way to handle plasma physics. I don't care how many Nobel prizes anyone has, if they say otherwise, they are absolutely wrong.

Unfortunately, you have no knowledge of your own to judge the value of my comments. All you can do is cut & paste what you don't understand, from sources nobody trusts. You are unlikely to learn a great deal that way. I can't reproduce entire textbooks that explain what I mean in hundreds of pages of physics. if you actually want to learn, why not go and study a real plasma physics textbook?

That's Alfven. I did not follow the link, and will not respond to it. I know the hosts of that site, and I know that they are idiots. Anyone who takes for granted anything that those people say is a fool.

Good question, and one that remains unanswered (though not unanswerable I think). But I doubt that the implications for particle physics are as fundamental as you think. The "standard model", for instance, is not one that I would call fundamental. It is little more than a spread sheet, with the cells occupied by observed quantities. But how does one fill in the blank cells?

To me, a "fundamental" concept is something that allows you to compute an expected value from first principles. But in the standard model, everything is an empirical extension of what's already there. It's an exercise in interpolation & extrapolation, but not derivation from more fundamental physical principles.

Baryonic matter is matter which couples with photons. Non baryonic matter will be anything that does not couple with photons. That's where the fundamental consideration lies for me. Why must all matter couple with photons? If we actually find non baryonic dark matter (WIMPS perhaps), the only real problem that the standard model will have with that is how to add cells to the spreadsheet. Besides, there is already a spot for the "neutralino" in predictions based on supersymmetry, which is in turn a key aspect of string theory.

You are the only one saying than I take all what this site say for granted because if it was the case I will not spend time confronting the theory.

I will accept your apologies for your last statement.

As to know who is right about MHD I think i will take the word of the inventor of the theory -it is easy to criticise- you do this very well at least about Plasma Cosmology.Even Einsten have done some flaws he have admit it however no one have stickin on that and rejected his work.

-TINY TIM -, I defied you to prove than Battener model don`t work if you replace MHD by the Bolzman and Maxwell equation in the two-dimensional model of magnetohydrodynamically driven rotation of spiral galaxies without dark matter. -Remember Battener is obviously not a plasma cosmologist this is why he apply MHD to all plasma.

http://adsabs.harvard.edu/cgi-bin/np...29B&db_key=AST

And don`t forget Thomas have the knowledge to verified your work.

But I am sure you are not willing to try that.

Why should I do all that work? You are the one who says it will work, so why don't you prove that it will work by doing it yourself?

And I will have you know that Tiny Tim is a respectable software package for simulating the point spread function of a telescope. Originally developed at the Space Telescope Science Institute, it is now being used to create model PSF's for SIRTF.

Good, I was sure than this was space related. I am still on topic. :wink:

I think the effect of finding such new particles would be pretty fundamental. The dimensionality of string/brane theory, as I recall, is directly related to the number of fundamental particles. Add more particles, and the theory almost has to start from scratch.