SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

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MrAmsterdam
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SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

Unread post by MrAmsterdam » Thu Dec 02, 2010 3:21 pm

SHEATH PHENOMENA IN DUSTY PLASMAS

Dutch rearch paper from the Technical University Eindhoven - 2005 by Gabriela Veselinova Paeva.

Paper discusses dust plasma phenomena and modelling the sheath phenomena plus the explanation of several experiments.

http://alexandria.tue.nl/extra2/200510434.pdf

Page 2 of the introduction reads;

Ionized gases containing small particles of solid matter are called dusty (com-
plex) plasmas
. In the last decades there has been a growing interest in this
¯eld. This interest rose in two very di®erent ¯elds in physics - the astro-
physics
and the industrial plasma research, in particular microelectronics.
Initially, the interest in dusty plasmas arose in the ¯eld of astrophysics,
as dust is present in many astrophysical environments (interstellar medium
[2], nebulae[3], comet tails, planetary rings [4])
. Another fundamental ¯eld,
in which the dust presence has an important role, is the physics of the atmo-
sphere
. Dust appears as aerosols in the atmosphere or as essential constituent
of the noctilucent clouds. Due to environmental awareness, this novel interest
is rising.
Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality. -Nikola Tesla -1934

jjohnson
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Re: SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

Unread post by jjohnson » Fri Dec 03, 2010 4:14 pm

Hi, Mr.A,
This is a well-researched paper, from reading through it. Dusty plasma is a fact of life in a wide variety of cosmic plasmas, as pictures of planetary nebula and the dusty lanes around galaxies reveal. I might venture a guess that dusty plasma may be more prevalent than a "pure" plasma in space conditions.

The paper made clear the balancing act of a levitating dusty plasma under lab conditions, in which a variety of forces is exerted upon the dust grains under test, including that of the local gravity. Peratt, in Physics of the Plasma Universe, (1992), Appendix C. Dusty and Grain Plasmas, formulates the general equation of motion in a plasma as
m dv/dt = mg + q(E + v x B) -m Vc v + f
where the g vector accounts for the total gravity forces present at the particle's coordinates, Vc is viscosity force summation, and f is the vector sum of all other forces, such as radiation pressure, ion drag, etc.

He notes that there are 4 cases, namely, Very Small Particles, where the second term q(E + v x B) dominates over the gravity term, mg; Small Grains, where q/m approximates sqrt(G), and where plasma effects still play a major role in system dynamics; Large Grains, an intermediate case where viscosity and gravity dominate, and their equation of motion is m Vc v = mg (which looks to me like the masses m should cancel out). His fourth case is Large Solid Bodies, the size of kilometers or more, for which the inertial and gravitational forces dominate the equations of motion. Peratt writes, "The transition of plasma into stars involves the formation of dusty plasma, the sedimentation of the dust into grains, the formation of stellesimals, and then the collapse into a stellar state [Alfvén and Arrhenius 1976, Alfvén and Carlqvist 1978]."

If Peratt's hypothesis is correct, understanding of dusty plasma dynamics is critical to the understanding the sequence of stellar formation if different from that of the Standard Model. Ms. Paeva's dissertation would seem to help this effort nicely.

Bellan, in Fundamentals of Plasma Physics, Chapter 17, Dusty plasmas, only considers the force of gravity at the end in 17.8 Student Assignments, in No.8. where he writes, "...by considering the combined effect of (i) the vertical electric field associated with this potential and (ii) gravity acting on a dust grain, show that dust grains will tend to levitate above the metal plate..." —virtually duplicating Ms. Paeva's experiment!

In the Dutch lab experiments by Ms. Paeva, the force calculated for gravity on the dust grains was very nearly the same as the levitating electric field force in her selected plasma conditions. I wonder, under remote conditions that may be parsecs from the nearest star or large body, if the resultant force of gravity from all sources in and around the dusty plasma mass or filament might be particularly small, and could be disregarded as a valid simplification. Peratt seems to think so, and claims that running particle-in-cell simulations with and without the gravity consideration demonstrates that.

Nonetheless, conditions where gravitational forces do become relevant, whether (1) as described as Large Solid Bodies or (2) in the well-known graph of the Bennet Relation to the right of the Jeans Criterion in cylindrical pinches where the plasma current I in the pinch region is in the range of 10^10 to 10^14 or so, and the number N of particles in the plasma is approximately > 10^43 per axial meter along the pinch, in the region annotated as "gravitationally balanced magnetic pressure", they must not be ignored, particularly as it is in plasma pinches and possibly instabilities (under EU concepts) where matter can be compressed and differentiated and heated into stars, whose own sheaths become the double layer represented by the chromosphere in our Sun.

Jim

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The Great Dog
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Re: SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

Unread post by The Great Dog » Sat Dec 04, 2010 1:43 pm

That was an informative synopsis.

TGD
There are no other dogs but The Great Dog

mharratsc
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Re: SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

Unread post by mharratsc » Sun Dec 05, 2010 2:01 pm

I can sort of follow what he says, but I am continuously amazed at how rapidly he puts it together and how concisely he can summarize.

I think he is some kind of cyborg-brain-guy... :shock:
Mike H.

"I have no fear to shout out my ignorance and let the Wise correct me, for every instance of such narrows the gulf between them and me." -- Michael A. Harrington

jjohnson
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Location: Thurston County WA

Re: SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

Unread post by jjohnson » Sun Dec 05, 2010 10:15 pm

Dang it, Mike, I'm an acoustician, not an astrophysicist. I just read the papers and guess, like everybody else.
Jim

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Re: SHEATH PHENOMENA IN DUSTY PLASMAS - 2005

Unread post by Solsearcher » Mon Dec 13, 2010 8:39 am

Dusty plasmas are thought to be the actual cause of tornadoes on earth!

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