Plasma Cosmology - Woo or not

http://subarutelescope.org/Pressrelease/2007/03/05/index.html "Researchers from the National Astronomical Observatory of Japan (NAOJ) and the University of Tokyo used Subaru's Suprime-Cam camera to discover an unusual streak of ionized hydrogen gas associated with a galaxy 300 million light-years from Earth. The filament of gas is only 6 thousand light-years wide, yet extends 200,000 light-years, about the distance between the Milky Way Galaxy and its companion, the Large Magellanic Cloud."

http://subarutelescope.org/Pressrelease/2002/04/index.html "Observations with Suprime-Cam on Subaru Telescope have detected for the first time long filaments of ionized hydrogen gas extending 110,000 light years above the disk of a galaxy. In the new image, the gas shows up in red and purple and appears to burst out of the center of the galaxy, reaching as far as the upper-left corner of the image. This galaxy, called NGC 4388, belongs to the Virgo Cluster, a large group of galaxies some 60 million light years from our own Milky Way galaxy."

http://chandra.harvard.edu/press/07_releases/press_092007.html "the comet-like tail was observed in X-ray light with NASA's Chandra X-ray Observatory and in optical light with the Southern Astrophysical Research (SOAR) telescope in Chile. The feature extends for more than 200,000 light years and was created as gas was stripped from a galaxy called ESO 137-001 that is plunging toward the center of Abell 3627, a giant cluster of galaxies."
I will have to add these to my list of plasma structures created from various energenic sources (e.g. black holes and galactic collisions). Of course anything less than a million lightyears in extent is not cosmic (not quite local but certainly within the sizes of galactic clusters).
 
Oh dear. Take a look at the scale invarience page at wikipedia, which shows the exact relationship I posted! they just use t instead of a to represent one of the variables; http://en.wikipedia.org/wiki/Scale_invariance#Scale_invariance_of_field_configurations

Oh dear indeed. So that incomprehensible nonsense was a completely garbled version of a wiki article you didn't understand?

If I take what you posted and replace a with t, curly delta with partial, lambda x -> lambda x' with t -> lambda t (so in other words if I change most of the symbols and equations), and I add the punch line (which you left off), I get something which shows that one of Maxwell's equations in vacuum is scale invariant. Sadly, after all that, Maxwell's equations in plasma are (obviously) NOT scale invariant, so this is completely irrelevant to your point.

Again, it's amazing how you post this stuff. You don't know the meaning of these terms and you don't understand either the notation or the meaning of the equations. You're a troll.
 
Ha! Go on then, say why this quote, taken from a mainstream publication from a respected journal is gibberish and maybe I'll believe you. I'm not holding my breath.

The quote you gave makes perfect sense. As usual with your quote-mining techniques, you took something which is correct in one context and applied it to another where it is totally wrong. That's what happens when you don't understand what you're reading.

That the sun would explode if it has a sufficient charge for EM forces to affect its motion (which is what we were discussing) follows immediately from Gauss' law. The fact that EM fields in a plasma may not fall off like 1/r^2, while true, is as relevant to that as the fact that people carry umbrellas when it rains.

As for that review, I glanced at it. It's quite cursory and gives few relevant details when it reviews the experiments. Moreover it reads like something written by someone with a political agenda. For example, it barely mentions the bullet cluster observation, which is absurd in a paper that devotes so much discussion to dark matter.

Moreover, many of the anomalies he mentions (which were quite intriguing) have recently gone away. Dark matter has now been detected directly; the case for its existence is now essentially closed. The Pioneer anomaly has been mostly explained by a sophisticated model of the heat exchange from the reactor. This makes it almost certain that nothing exotic is going on there.

Basically, we have very strong theoretical reasons to believe that general relativity is correct at long distances, but that it is incorrect at short distances (shorter than current experiments can probe). Moreover we have no experimental evidence against that - on the contrary, we have extremely strong support for it across all scales. The biggest mystery is dark energy, but that should properly be thought of as a prediction of GR. Explaining the size of the cosmological constant is a tremendous challenge, but one that probably falls outside the purview of any theory of low energy physics (certainly one should not expect GR alone to explain the values of its two parameters).

Does this mean the case is closed, and GR is correct? Almost certainly yes, but it is still worth looking for alternatives, particularly in view of the mystery of dark energy.
 
Dark matter has now been detected directly;

Hi Sol
Wouldn't it be more correct to say that the effect of dark matter has been directly detected. As yet we still do not know what dark matter is or what it consists of. To say that dark matter has been directly detected implies that we can actually observe dark matter and know what it is having directly observed or detected it. just a thought.
 
Hi Sol
Wouldn't it be more correct to say that the effect of dark matter has been directly detected.

I'm not sure there's really a distinction there. For example, would you say stars (other than the sun, say) have been directly detected, or only their "effects"? How about air? Quarks?

We're used to thinking of EM radiation - specifically, light - as direct, since we can see it ourselves. And in fact DM was recently seen through its gravitational effects on light, in rough analogy to the way one can "see" air shimmering near a hot surface on a hot day. That's pretty darn direct. Of course it has also been detected in many, many other less direct observations as well.

It's certainly true that we do not know much about what DM consists of. However we know a fair amount about its gross properties - its total mass, its level of interactions with EM radiation, its self-interactions, its temperature, etc. Mmuch remains to be discovered, but its existence is all but indisputable and its basic properties reasonably well known.
 
I'm not sure there's really a distinction there. For example, would you say stars (other than the sun, say) have been directly detected, or only their "effects"? How about air? Quarks?

Hi Sol

Sure, the existence of dark matter is not under dispute. Either there is dark matter or all the theories of gravitation are wrong. My bet goes to dark matter.
As far as stars are concerned, you can see them, analyse the light spectra and infer "prove" what its constituents are, same with air, you can go to the gas company and buy bottles of all the different constituents of air. This makes them directly detectable.

This criteria cannot be applied to dark matter. I realise that the crux of the issue is choice of words, but I think that "direct proof of the effect of dark matter" is more appropriate. To date, the direct proof of dark matter in the lab is yet to be announced, although it is probably not too far away.

Quarks on the other hand, cannot exist in isolation , yet can be inferred through experiment.
 
Hi Skwinty
The evidence for dark mater is a direct observation as astronomers define direct. For example people are used to seeing light and so treat telescopic observations as direct. But an astronomer will also treat radio, infrared and x-ray observations as direct even though they are not "directly" observed. In the case of the Bullet Cluster there are 2 observations that are considered direct:
  • The hot gas detected via x-rays.
  • Matter detected by gravitational lensing.
The separation between the areas of hot gas and matter shows that the matter was not affected by the collision, is massive and dark (fits the properties of dark matter).
 
Hi Reality Check and Sol
Yes, I take your points about direct observations etc.
I suppose its 6 of one and half dozen of the other. My next question, though would be:
What do these direct observations say about dark matter other than their effect on their surrounds? I suppose I interprete direct proof of dark matter to be that the proof states the constituents or composition of dark matter which it does not.
It only states that dark matter must exist because of effects x,y and z.
 
Hi Reality Check and Sol
Yes, I take your points about direct observations etc.
I suppose its 6 of one and half dozen of the other. My next question, though would be:
What do these direct observations say about dark matter other than their effect on their surrounds? I suppose I interprete direct proof of dark matter to be that the proof states the constituents or composition of dark matter which it does not.
It only states that dark matter must exist because of effects x,y and z.
Basically the Bullet Cluster observation says that there is a massive amount of matter there that is dark and does not interact strongly with other matter. The strength of the interaction can be used to guide us to what dark matter actually is, what the chances are of locating it locally and puts limits on theories of Modified Newtonian Dynamics.
 
Hi Sol
Wouldn't it be more correct to say that the effect of dark matter has been directly detected. As yet we still do not know what dark matter is or what it consists of. To say that dark matter has been directly detected implies that we can actually observe dark matter and know what it is having directly observed or detected it. just a thought.


This is a cogent point but it applies to so much of science.

The dark matter theory is supported by the bullet cluster observation, to an accurate degree.

When a competing theory comes along that also explains the bullet cluster observation to an equaly accurate degree then there will be competition,

BTW a belated Welcome!
 
Zeuzzz, would you care to do the following:
1) Calculate the ratio of the EM charge to the mass for a proton.
2) Calculate the ratio of the gravitational charge to the mass for a proton.
3) Calculate the ratio of the EM charge to the mass for a stellar object.
4) Calculate the ratio of the gravitational charge to the mass for a stellar object.
5) Draw conclusions about scale invariance of the two forces from your answers to 1 to 4.
 
Redshifts, etc

Tidying up a loose end ...

One of the many inconsistencies that makes PC, as presented in this thread by Z, woo is redshift.

Actually, it's a set of related inconsistencies.

Start with observation: for galaxies (and other objects) beyond the Local Group (the MW, M31, M33, the Magellanic Clouds, etc), distance and redshift are closely related - the greater the redshift, the greater the distance. This was first noticed by Hubble*, nearly a century ago now, and the distance-redshift relationship is today called the Hubble relationship. There's some scatter about the trend line, and a quantitative measure of that scatter correlates well with the objects membership of groups and clusters (the richer the cluster, the greater the scatter). To the extent that they have been measured, redshifts in different wavebands are the same (for the same object) - a galaxy's redshift measured in the x-ray waveband is the same as it is in the UV, or IR, or microwave, or radio waveband. Further, the atomic (or molecular) transitions that give rise to the lines used to measure redshift are many, from highly ionised iron, to moderately ionised oxygen, to neutral CO and H; hence the physical environments in which the excited species exist span an amazing range of temperature, density, and so on. Those are the observational results.

As Plasma Cosmology (PC) is universal in its scope (at least according to Z, per his posts in this thread), a good, consistent (PC) explanation of these observations should be available.

Surprisingly, there is no such explanation.

Instead (per Z anyway) there is a mishmash of creative ideas, speculations, and nonsense, with no apparent attempt by any PC proponent to produce anything definitive.

Curiously, most of these PC explanations involve mechanisms or processes that have never been seen in any lab here on Earth, a fact which would, no doubt, cause Alfvén to turn in his grave (a more egregious violation of his actualistic approach would be hard to imagine!); the ones that have been observed in labs pretty obviously do not apply to galaxies or objects whose redshifts have been measured in widely separated wavebands (say, radio and visual).

Even more curious, perhaps, is how uncritically PC proponents (including Z) embrace the published papers of Arp, Bell, et al ... curious because (among other things) there's even less in the way of potential (plasma) mechanisms for Arpian 'intrinsic redshift' than there is for that of the Hubble relationship**, and because if there really were such 'intrinsic redshifts' most of the works of most PCers (such as Peratt and Lerner) would have to be extensively edited, if not completely re-written.

In a way, the uncritical acceptance of Arpian 'intrinsic redshifts' for quasars is a rather nice summary of PC as a whole: not only are there no papers by any of the founders of PC on the existence of such an effect (recall that PC proponents are very big on 'predictions'), not only are there no plasma-based mechanisms for such an effect, but PC proponents are quite unconcerned about lensed quasars, which provide about as clear an observation-based case as you could ask for that quasars are at distances consistent with their (Hubble relationship) redshifts (example)!

Saying this another way: uncritical acceptance of inconsistencies, of many kinds and at many levels (and the extreme reluctance to even acknowledge that any inconsistencies exist), shows that whatever PC is, it is not a science or based on science.

Can we get on to new questions now? Like whether PC is more akin to religion or to conspiracy theories?

* actually it was almost certainly noticed by someone else earlier, but Hubble gets the credit (for being the first to publish a paper on it?)

** with one exception: AFAIK it is possible (and maybe even easy) to construct models for some subsets of the line spectra of unresolved quasars using standard physics; however such models are inconsistent with more general observations of quasars
 
(bold added)
[...]

As for that review, I glanced at it. It's quite cursory and gives few relevant details when it reviews the experiments. Moreover it reads like something written by someone with a political agenda. For example, it barely mentions the bullet cluster observation, which is absurd in a paper that devotes so much discussion to dark matter.

Moreover, many of the anomalies he mentions (which were quite intriguing) have recently gone away. Dark matter has now been detected directly; the case for its existence is now essentially closed. The Pioneer anomaly has been mostly explained by a sophisticated model of the heat exchange from the reactor. This makes it almost certain that nothing exotic is going on there.

Basically, we have very strong theoretical reasons to believe that general relativity is correct at long distances, but that it is incorrect at short distances (shorter than current experiments can probe). Moreover we have no experimental evidence against that - on the contrary, we have extremely strong support for it across all scales. The biggest mystery is dark energy, but that should properly be thought of as a prediction of GR. Explaining the size of the cosmological constant is a tremendous challenge, but one that probably falls outside the purview of any theory of low energy physics (certainly one should not expect GR alone to explain the values of its two parameters).

Does this mean the case is closed, and GR is correct? Almost certainly yes, but it is still worth looking for alternatives, particularly in view of the mystery of dark energy.
It gets better ...

The link Z gives is to v2 of a preprint in arXiv; it's now up to v7, and well over a year since it first appeared (and apparently still hasn't been accepted for publication) ... usually a sign that there are rather a lot of problems with the paper ....
 
Hi Reality Check and Sol
Yes, I take your points about direct observations etc.
I suppose its 6 of one and half dozen of the other. My next question, though would be:
What do these direct observations say about dark matter other than their effect on their surrounds? I suppose I interprete direct proof of dark matter to be that the proof states the constituents or composition of dark matter which it does not.
It only states that dark matter must exist because of effects x,y and z.
You might find this JREF Forum thread of interest:

Non-baryonic cold dark matter ("CDM"), the observational evidence
 

Hi DRD
Very interesting, I have saved the thread for further digestion.
Still seems to me though the evidence relates to the effects rather than dark matter itself. Sure, the inferences about dark matter are there.
I suppose that when dark matter is produced in the lab, which hopefully will be soon then clarity will prevail in the dark recesses of my knowledge base. I dont dispute the existence of CDM just expressing some doubt as to the definitive headlines that one sees in publications.
Also as Carl Sagan said, extraordinary claims require extraordinary evidence. Thanks for the fine effort at explaining all the finer points of CDM.
 
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Hi DRD
Very interesting, I have saved the thread for further digestion.
Still seems to me though the evidence relates to the effects rather than dark matter itself. Sure, the inferences about dark matter are there.
I suppose that when dark matter is produced in the lab, which hopefully will be soon then clarity will prevail in the dark recesses of my knowledge base. I dont dispute the existence of CDM just expressing some doubt as to the definitive headlines that one sees in publications.
Also as Carl Sagan said, extraordinary claims require extraordinary evidence. Thanks for the fine effort at explaining all the finer points of CDM.
(bold added)

First, why not ask about this in that thread itself? After all, this one is supposed to be about Plasma Cosmology and whether it is woo or not (do you have something to add to that question, BTW)?

Second, doesn't "the evidence relates to the effects rather than dark matter itself" cover just about all of astronomy (beyond the solar system)? For example, what are spectroscopic binaries? eclipsing binaries? neutron stars (NS)? white dwarf (WD) stars? the [OIII] 500.7 nm emission line? the 21-cm HI line?

In which lab has even the [OIII] 500.7 nm line been observed (much less a 10g chunk of WD or NS matter)?

And it doesn't have to be forms of mass ... how about 10^9 T magnetic fields? or particle accelerators that can produce 10^20 eV protons?
 
Sol, what do you make of these publications, which show numerous long distance EM forces in plasmas on the large scale that are comparable, if not stronger on occasions, to gravity?

[Peratt references]


(fourth time with no comment)
As RC has already noted, these have been commented on extensively already, both in this thread and others.

Also, I think you'll find - when you get around to actually reading them - that several of the >30 posts of mine I listed earlier contain direct questions to you about at least one of these documents, as well as commentary on the extent to which this work of Peratt falls short of being realistic ... in other words, Peratt may be modelling a universe, but it is not the one that we happen to live in ...
 
I will have to add these to my list of plasma structures created from various energenic sources (e.g. black holes and galactic collisions).

Guess you missed this from the second source:

"these new results are puzzling as the energy produced by the black hole can only ionize gas for a distance of 50,000 light years."
 
I'm not sure there's really a distinction there. For example, would you say stars (other than the sun, say) have been directly detected, or only their "effects"?

We actually see the sun because of the light generated by it. The same cannot be said for dark matter. We have NOT seen it. We don't know what it is. Even after decades and decades and decades. You only INTERPRET the motions you SEE as being the result of dark matter. But perhaps your interpretation is flawed. Perhaps you're holding the trunk and calling it a tree when in fact it's an elephant.
 
In the case of the Bullet Cluster there are 2 observations that are considered direct:

• The hot gas detected via x-rays.
• Matter detected by gravitational lensing.

Hot gas emitting x-rays can exist for a variety of reasons that have nothing to do with dark matter. By the way ... it's not gas ... it's plasma. And gravitational lensing calculations are based on a number of assumptions. Which may or may not be right.
 
Hot gas emitting x-rays can exist for a variety of reasons that have nothing to do with dark matter. By the way ... it's not gas ... it's plasma. And gravitational lensing calculations are based on a number of assumptions. Which may or may not be right.
Have you ever read about the Bullet Cluster?
The hot gas is not the dark matter. It is the gas that has been heated by the collision of the clusters.
List the assumptions in gravitation lensing and why they may not be correct. N.B. If you read the original paper then you will see that the calculation does not depend on the distance to the Bullet Cluster.
 
We actually see the sun because of the light generated by it. The same cannot be said for dark matter. We have NOT seen it. We don't know what it is. Even after decades and decades and decades. You only INTERPRET the motions you SEE as being the result of dark matter. But perhaps your interpretation is flawed. Perhaps you're holding the trunk and calling it a tree when in fact it's an elephant.
We have seen dark matter because of the bending of light (micro-gravitational lensing). This is as good an observation as the light that we see the sun by, the radio waves used in radio telescopes or the many other techniques that astrononmers use to observe the universe.
The rotations of galaxies and motions of galaxies within galactic clusters were just the beginning of the evidence for dark matter. Your knowledge seems to be "decades and decades and decades" out of date.

A local observation that supports the existence of dark matter: Dwarf galaxies in the Local Group are 400 times more massive than their visible matter.
 
Hot gas emitting x-rays can exist for a variety of reasons that have nothing to do with dark matter.
Indeed.

In the case of rich (relaxed) clusters, do you have an explanation for the quantitative observations of the hot gas/plasma that does NOT involve CDM?

I mean a consistent explanation ...
By the way ... it's not gas ... it's plasma. And gravitational lensing calculations are based on a number of assumptions. Which may or may not be right.
Yep ...

... just like the rest of astronomy ...
 
Dwarf galaxies in the Local Group are 400 times more massive than their visible matter.

Wow ... that gnome just keeps getting more and more important.

By the way, did you notice this statement in your source:

By knowing the minimum volume that dark matter can occupy, the researchers were able to calculate other physical properties of dark matter. One of these properties was speed, which turned out to be about 6 miles per second (9km/s). "That's about a million times faster than predictions," Gilmore said in a telephone interview.

Only off by a million times? That's some predictive theory you have. :rolleyes:
 
Beacuse gas is more a general term than plasma and includes plasma. ;)

Plasma is distinguished from gas BY SCIENTISTS because it has very different properties. And the fact that the mainstream (and you) insist on repeatedly calling material gas that is in fact plasma is perhaps part of the problem the mainstream and you are having with understanding the nature of the universe. :)
 
Plasma is distinguished from gas BY SCIENTISTS because it has very different properties. And the fact that the mainstream (and you) insist on repeatedly calling material gas that is in fact plasma is perhaps part of the problem the mainstream and you are having with understanding the nature of the universe. :)
The problemm is determining whether what we are observing is a plasma or just an ionized gas. If we do not know then calling it a gas is safer since that term includes plasma. Perhaps you know the ionization and Debye length parameters of the hot gas detected in the Bullet Cluster. If you do then share it with us and then we can see if it is a plasma or not. Personally I think that it is a plasma but I am not sure and so I follow the standard practise of calling it a hot gas.
 
Wow ... that gnome just keeps getting more and more important.

By the way, did you notice this statement in your source:



Only off by a million times? That's some predictive theory you have. :rolleyes:
Huh?

I thought this thread was about Plasma Cosmology ... am I mistaken?

If not, then can you please provide a consistent, quantitative explanation for the observations (of the dwarf galaxies) that is built from first (plasma physics) principles? Preferably one that is contained in a paper (or three) published in a relevant peer-reviewed journal ...
 
Plasma is distinguished from gas BY SCIENTISTS because it has very different properties. And the fact that the mainstream (and you) insist on repeatedly calling material gas that is in fact plasma is perhaps part of the problem the mainstream and you are having with understanding the nature of the universe. :)
OK ...

And for the gas/plasma in question (that which pervades rich clusters of galaxies), what - specifically and quantitatively - are the differences in those properties (gas vs plasma), as they pertain to astronomical observations of those clusters, or potential observations of those clusters?
 
Wow ... that gnome just keeps getting more and more important.

By the way, did you notice this statement in your source:



Only off by a million times? That's some predictive theory you have. :rolleyes:

Unlike your unsbstantiated speculation and groping after tidbits of information.

care to put any of your pet theories to the number test?

I offer sincerely to you, you name the object, the mass, the charge and change in velocity that can be accounted for in the EM forces of the 'flat rotation curves of galaxies'. So far we have zilch from Zeuzzz, do you want to try.

It is a great idea, as many ideas are , however it has yet to be applied to reality.

Or would you rather I just ask the seven questions that you won't answer again. This being a polite version of number two question.

You haven't shown anything that would substantiate the Perrat model of galaxy rotation, nor has Zeuzzz.

(Welcome back BTW :) )
 
Plasma is distinguished from gas BY SCIENTISTS because it has very different properties. And the fact that the mainstream (and you) insist on repeatedly calling material gas that is in fact plasma is perhaps part of the problem the mainstream and you are having with understanding the nature of the universe. :)

Like this pop snippet of mainstream science:

http://www.sciencedaily.com/releases/2008/07/080703113646.htm

There are plenty of sources that use the term plasma all the time. It is amazing how you focus on the 'does an angel wear tights' kind of question rather than showing that your theories mean anything.

:)
 
The problemm is determining whether what we are observing is a plasma or just an ionized gas.

ROTFLOL! The definition of a plasma is "ionized gas".

http://physics.about.com/od/glossary/g/plasma.htm - Definition: Plasma is a distinct phase of matter, separate from the traditional solids, liquids, and gases. It is a collection of charged particles that respond strongly and collectively to electromagnetic fields, taking the form of gas-like clouds or ion beams. Since the particles in plasma are electrically charged (generally by being stripped of electrons), it is frequently described as an "ionized gas."

http://www.scala.com/definition/plasma.html - Just as solids, liquids and gases are states of matter, plasma is a state of matter. Specifically, plasma is ionized gas. That is, gas that has been given an electrical charge by being stripped of electrons.

http://space.about.com/od/glossaries/g/plasma.htm - Definition: plasma: A low-density gas in which the individual atoms are ionized ...

http://en.wikipedia.org/wiki/Plasma_(physics) - In physical and chemical usage, plasma refers to an ionized gas, in which a certain proportion of electrons are free, rather than being bound to an atom or molecule.

And how many times have we discussed that here at JREF in threads you were present?
 
ROTFLOL! The definition of a plasma is "ionized gas".

http://physics.about.com/od/glossary/g/plasma.htm - Definition: Plasma is a distinct phase of matter, separate from the traditional solids, liquids, and gases. It is a collection of charged particles that respond strongly and collectively to electromagnetic fields, taking the form of gas-like clouds or ion beams. Since the particles in plasma are electrically charged (generally by being stripped of electrons), it is frequently described as an "ionized gas."

http://www.scala.com/definition/plasma.html - Just as solids, liquids and gases are states of matter, plasma is a state of matter. Specifically, plasma is ionized gas. That is, gas that has been given an electrical charge by being stripped of electrons.

http://space.about.com/od/glossaries/g/plasma.htm - Definition: plasma: A low-density gas in which the individual atoms are ionized ...

http://en.wikipedia.org/wiki/Plasma_(physics) - In physical and chemical usage, plasma refers to an ionized gas, in which a certain proportion of electrons are free, rather than being bound to an atom or molecule.

And how many times have we discussed that here at JREF in threads you were present?
In physical and chemical usage, plasma refers to an ionized gas, in which a certain proportion of electrons are free, rather than being bound to an atom or molecule.

Also
<H3>Definition of a plasma
Although a plasma is loosely described as an electrically neutral medium of positive and negative particles, a definition can have three criteria:[8][9][10]
  1. The plasma approximation: Charged particles must be close enough together that each particle influences many nearby charged particles, rather than just interacting with the closest particle (these collective effects are a distinguishing feature of a plasma). The plasma approximation is valid when the number of electrons within the sphere of influence (called the Debye sphere whose radius is the Debye screening length) of a particular particle is large. The average number of particles in the Debye sphere is given by the plasma parameter, "Λ" (the Greek letter Lambda).
  2. Bulk interactions: The Debye screening length (defined above) is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, where boundary effects may take place.
  3. Plasma frequency: The electron plasma frequency (measuring plasma oscillations of the electrons) is large compared to the electron-neutral collision frequency (measuring frequency of collisions between electrons and neutral particles). When this condition is valid, plasmas act to shield charges very rapidly (quasineutrality is another defining property of plasmas).
</H3>
 
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