User:Aarghdvaark/scratch

Peratt work in progress

 * The Peratt instability in  plasma physics is named after him.

Adam Nailor
search on "Adam Nailor plasma cosmology": Talk%3APlasma_cosmology/Archive_9

Lerner's suggestion of what was a good article on Plasma cosmology

Comparison BBT and PC, and a go at defining PC

Joining of space plasma filaments


One of the most basic and important concepts in plasma cosmology is how plasma filaments combine together in pairs. Because of the scalability of plasma effects, this is something which can be demonstrated here on Earth, e.g. with a plasma globe, but yet, it is claimed by plasma cosmology proponents,  the same mechanism applies on all scales and can be seen e.g. in aurora, stellar formation, and galaxy formation.

This explanation is based on one by Lerner, and assumes an existing magnetic field and two plasma filaments, aligned along the magnetic field lines and each carrying an axial electric current opposite to the magnetic field (i.e. Birkeland currents), and for simplicity ignores gravity:
 * The currents in the two filaments will produce circular magnetic fields around them, which interact with the current in the other filament to generate a force attracting the two filaments together (use the right hand rule to determine the direction of the magnetic field.
 * Then Fleming's left-hand rule to show each filament is attracted to the other, i.e. "like" currents attract).
 * However, as the filaments move towards each other, the original (or background) external magnetic field and the motion interact to cause a current across the filaments (use Fleming's right-hand rule, N.B. not the same as the "right hand rule" used before). The current is composed of protons moving in the direction of the current and electrons moving in the opposite sense. The electrons and protons that form this current will congregate at opposite sides of the filament.
 * Using Fleming's right-hand rule again, the filament motion interacts with the circular magnetic field surrounding the other filament, causing a secondary current to flow at the filament edges, in the opposite direction to the main current.

Since the electrons move much faster than the protons, the current profile across the filaments will be unbalanced, which means the attraction between the filaments is now offset from their centres. As the two filaments move towards and past each other, the excess charges on the inner faces of the filaments will repel each other as they are like charges. Collision does not occur because the repulsive force from the like charges on the inner surfaces of the filaments exceeds the attractive force from the main (like) currents. "At this time the translational momentum is converted into angular momentum because of the ... torque between filaments". The two filaments become twisted together into a rotating double filament, which acts as if it were a single filament and can combine with another filament in the same way. Thus plasma filaments tend to "pinch" together, this being an example of a z-pinch since the current is in the z-direction with an azimuthal magnetic field.

Birkeland currents are self-constricting or self-focussing. This is because in some regions of its current versus voltage characteristics a plasma exhibits negative resistance, i.e. the higher the current the lower the resistance. A lower energy state is therefore achieved when the current density is increased by decreasing the cross-sectional area of the current carrying plasma. Hence a filament will narrow, and if emitting light as in a plasma globe it will brighten. Eventually a minimum point is reached where the resistance begins to rise, stopping further constriction.

Joining of space plasma filaments: talk
not surprising, since originally we used Fleming's left-hand rule for motors to determine the direction of motion, finally we used Fleming's right-hand rule for generators, in the same field, to determine the direction of this secondary current

formatted explanation to make it easier to read

Helicity has nothing to do with angular momentum. It is the twist or topological linkage of (field-aligned) currents. Apart from the fact that it doesn't address this particular problem, Perrat's statement doesn't make any sense. A torque produces angular momentum, it doesn't "convert" linear momentum into angular momentum. If this section is based on Perrat's paper, then it is no wonder that it is confusing, because the paper is also confusing. As far as I can tell, the paper does not address the question of whether the simulation conserves angular momentum. The illustration in the article show two filaments winding around each other. Perrat's filaments do not do that and cannot do that because he only simulates a thin slice.
 * The whole section is not based on Perrat's paper - please, please, read what is written.

If a filament carries an "enormous currents" after it forms from smaller filaments, then those filaments must already have carried this "enormous current" before combining. (Has been deleted. Art Carlson (talk) 12:01, 18 May 2012 (UTC))

"as the filaments move towards each other, the original (or background) external magnetic field and the motion interact to cause a current across the filaments" Is this referring to the minimal charge separation of a plasma moving in a magnetic field? the current that is almost immediately stopped by the electric field it produces? "Using Fleming's right-hand rule again, the filament motion interacts with the circular magnetic field surrounding the other filament, causing a secondary current to flow at the filament edges, in the opposite direction to the main current (not surprising ..." I can't tell whether this is surprising or not because I can't understand it.

"Since the electrons move much faster than the protons, the current profile across the filaments will be unbalanced" If this is referring to the ExB drift, then that is the same for electrons and ions. If it is referring to the motion along the field, then it will produce no charge separation. "the repulsive force from the like charges on the inner surfaces of the filaments" I haven't figured out why there should be an excess charge on the inner surfaces, but if there is, why doesn't it just cause a further redistribution of the charge? "The two filaments become twisted together into a rotating double filament" There are processes which can change the helicity (twist) of the currents, but none of them has been introduced here. The effect of concentration due to resistivity feedback exists, but it is not the effect commonly called a pinch, and it does not produce a concentration of mass. I have never seen any claim that the resistivity effect is important in plasma cosmology.

ambiplasma
ambiplasma - how to separate charges

plasma cosmology definition
In 1937, Alfvén argued that if plasma pervaded the universe, it could then carry electric currents capable of generating a galactic magnetic field. After winning the Nobel Prize for his works in magnetohydrodynamics, he emphasized that: "In order to understand the phenomena in a certain plasma region, it is necessary to map not only the magnetic but also the electric field and the electric currents. Space is filled with a network of currents which transfer energy and momentum over large or very large distances. The currents often pinch to filamentary or surface currents. The latter are likely to give space, as also interstellar and intergalactic space, a cellular structure."

Any definition of Plasma Cosmology must be based on verifiable reliable sources. Hannnes Alfvné's paper "Cosmology in the plasma universe - an introductory exposition" (1990) notes (edited for format):
 * "The basic aspects of cosmological importance are:
 * (1) the same basic laws of plasma physics hold everywhere;
 * (2) mapping of electric fields and currents is necessary to understand cosmic plasma;
 * (3) space is filled with a network of currents leading to the cellular and filamentary structure of matter; and
 * (4) double layers, critical velocity, and pinch effects are of decisive importance in how cosmic plasma evolves." (Full paper here) (1990)


 * Other information about Plasma Cosmology can be found in these papers by Alfvén (both online): (1) "On hierarchical cosmology" (1983). (2) "Cosmology - Myth or science?" (1984). And these papers by Peratt (also online): (3)  "Plasma Cosmology", (1992). (4) "Not With A Bang" (Part A | Part B) (1990)".
 * It is clear that Plasma Cosmology includes standard astrophysical plasma physics (indeed, it relies on it) --Iantresman 12:33, 10 December 2006 (UTC)

Intergalactic magnetic field
''Additionally gravity is important at large scales, magnetic forces are important in plasma since magnetic forces, like gravity, cannot be shielded. For example, in the Local Supercluster of galaxies, the magnetic field is 0.3 microgauss over a volume 10 Mpc in radius centered on the Milky Way. ''

As I've said before, this paragraph is extremely problematic. Here's the issue: Kronberg is on the high-end of magnetic field measurements for intergalactic space. A quote from a popular-level article:


 * "I'm surprised, very surprised," says Russell M. Kulsrud of Princeton University, adding that he harbors some doubts that the strengths "are quite as high as [Kronberg] said." But even if the field strengths are a bit smaller, he adds, "they are still . . . very difficult to explain."



This is an open question and to propose it as a bald fact like this is extremely problematic. Therefore I have removed this per reliable source and verifiability concerns. --ScienceApologist 06:58, 15 December 2006 (UTC)

peer reviewed text removed by SA because he didn't think author qualified
Writer Jeff Kanipe wrote in Astrophysics and Space Science, that::"Plasma cosmology sprang from the pioneering work of Hannes Alfven. Stemming from his studies in the 1950s of synchrotron radiation—emission caused by electrons spiraling at nearly the speed of light in a magnetic field (Alfven and Herlofson, 1950b), Alfven proposed that sheets of electric currents must crisscross the universe (Alfven, 1950a; Alfven and Carl-Gunne_Fälthammar, 1962, ). Interaction with these electromagnetic fields would enable plasmas to exhibit complex structure and motion. Thus, at the grandest scales, the universe would have a cellular and filamentary structure."

rediscovered commentary
While highly suggestive and possibly applicable to galaxy formation, Peratt's model does not describe the majority of the visible mass of developed galaxies, which is in the form of stars. Art Carlson

Traffic flow (computer networking)
As packets traverse successive communication links towards their destination, the packets from one flow (e.g., A1, A2, A3) will be intermingled with packets from other flows also traversing the network to form a multiplexed stream (e.g., A1, B7, C9, A2, C10, A3). This represents a form of statistical multiplexing because the link is shared as required.

The term flow is often used synonymously to a multiplex channel

Galaxy rotation curve
There are a limited number of attempts to solve the problem of galaxy rotation curves without invoking dark matter. These are not considered mainstream scientific theories.


 * Modifying gravity

In 2005 Cooperstock and Tieu posted a preprint of an article which claimed that, using general relativity rather than Newton's law of universal gravitation, "the rotation curves for the Milky Way, NGC 3031, NGC 3198 and NGC 7331 are consistent with the mass density distributions of the visible matter concentrated in flattened disks. Thus the need for a massive halo of exotic dark matter is removed". This was followed by further work (e.g.  ) and by Cooperstock writing a book on the subject. However this theory has come in for criticism (e.g.  ). The main problem for many astrophysicists with this idea is that they believe there is no need to go beyond Newtonian gravity and indeed that a relativistic solution should match the Newtonian solution, whilst proponents of the theory say the case of a galaxy is a fundamentally different problem from that of the solar system, where "the dominant field is that of the sun and the planets are for most purposes properly treated as test particles in the solar field, guided by this field but not contributing to the global field. By contrast, in the galactic problem, the elements of matter are both guided by and essential contributors to the global field".
 * Applying general relativity instead of Newtonian gravity
 * Other factors

further thoughts: "If gravitation does not follow an inverse square law on large scales or in complex systems, this is a strong clue that gravitation is an emergent force and not a fundamental one. Many smart fellows, including Sakharov and Feynman, believed that the "fundamental" properties of matter arise from interaction and are not innate to the material body. Others today like Puthoff, Rueda and Haisch are exploring this, as well".

Virial theorem