Recovered: Dusty Plasmas

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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Fri Jul 11, 2008 9:08 pm

Junglelord wrote:Some one today thought longitudinal current was bunk. They also thought its a discredit to science to even talk about it.


You have to explain this in more detail, if you could please. Bunk and discredit are big words. :shock:
discrediting science :) by talking about something :D :lol:

Junglelord wrote:You know why Tesla had that spiral coil? To transmitt. That is longitudinal transmission.

Transmission of power.

Junglelord wrote:We are talking about coherent non linear energy transmission that is massive, we are not talking transverse, we are talking longitudinal in these regards. It is well known that hurricanes and tornados are spiral, they are also longitudinal forms. Longitudinal waves present as they are "longitudinal" ie tsunami or as a vortex ie hurricane tornado.

In this thread below there are three posts that also are connected to this:
The first one gravity waves enhancing tornado systems, the second about noctilucent clouds as mentioned some posts up and a thundercloud electrification-model that has some words in it that might be familiar to you, Dean. ;)
Addendum: Waterspouts, landspouts and dust devils (part II)
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Tue Jul 15, 2008 2:12 pm

Max Planck Institute for Extraterrestrial Physics

- Theory & Complex Plasmas -

Project: Plasma Crystal
Plasma Crystals form under certain conditions in a complex ("dusty") plasma. There, the electrically charged dust particles arrange in a regular macroscopic crystal lattice. This allows the investigation of the properties of condensed matter on the most fundamental level, the kinetic one. This means that basic processes, such as melting, can be followed by observing the motion of individual particles. Since plasma crystals were discovered in 1994 the interest in this research area - in theory and experimentally - has grown exponentially.
Image
The image to the right shows the sideview of a plasma crystal in the laboratory. Dust particles are suspended in an argon plasma above a high-frequency electrode (bottom). The horizontal field of view is 1 cm. If you touch the image with the mouse pointer you will see a view of one crystal lattice. (Javascript must be activated.)

Gravity plays an crucial role for the structure of plasma crystals. In ground-based lab experiments mainly 2-dimensional crystals can be observed. This is due to the sedimentation of the micron-sized particles which build up the crystal.

In microgravity big 3-dimensional plasma crystals can be grown. Therefore, our institute deals - besides ground-based lab research - with the investigation of plasma crystals under microgravity conditions, e.g. on parabolic flights and rocket experiments.
http://www.mpe.mpg.de/theory/plasma-crystal/index_e.html

''Plasma Crystal''

Scientific Background
A plasma - an ionized gas consisting of electrons and ions - is the fourth state of matter and, besides solid (crystalline), liquid and gaseous, also the most disordered state. Plasmas exist mainly at high temperatures and expose a good electric conductivity. In our daily life we see plasmas in the flame of a candle, in the illuminating gas of neon lights, or in the shining surface of our sun. More than 99% of the visible matter in our universe is in the plasma state.
Image
Particles under the mikroscope The crystallization of a plasma - without losing the plasma state - can be achieved with an additional component: micro-particles or 'dust'. These particles (actually melamine-formaldehyde spheres provided by externalMicroparticles GmbH, see microscopic image) with the size of several microns (1 µm = 1/1000 mm) get charged inside the plasma by the bombardment with free electrons and ions. Due to the much lower mobility of the heavier ions, the particles are hit on average by more electrons. They accumulate a negative charge of several 1000 - 10,000 electron charges. This negative charge is, at a certain distance, screened by a positive cloud of ions around the particle. (See figure below.)
Image
At a certain particle density the particles start to interact with each other by the repulsive Coulomb force. Together with the surrounding plasma they form a so-called 'complex (dusty) plasma'. The interaction may lead to a strong coupling of the particles, resembling a fluid phase, and even to the crystallization of the particles with a typical spacing of some 1/10 mm in a so-called 'plasma crystal'. Compared to the size of the particles the inter-particle spacing in a plasma crystal is large.

In general, the properties of complex plasmas and plasma crystals offer a variety of unique opportunities:

* Particles can be observed individually. (Much simpler than e.g. the atoms of a crystal lattice.) This allows the investigation of multi-particle systems at the kinetic level.
* Timescales are stretched due to the high mass of the particles (compared to the mass of single atoms). This results in a high time resolution of the observed processes.
* Particles can individually be controlled and manipulated. This allows 'active' experiments.

This offers a totally new access to the physics of condensed matter and plasma physics.

Image


http://www.mpe.mpg.de/theory/plasma-crystal/index_e.html


This is a nice site with good links.
The illusion from which we are seeking to extricate ourselves is not that constituted by the realm of space and time, but that which comes from failing to know that realm from the standpoint of a higher vision. -L.H.
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Tue Jul 15, 2008 2:56 pm

The group Elementary Processes in Gas discharges (EPG) focuses on technological plasmas. We want to obtain a better understanding of these scientifically challenging non-equilibrium systems. Meanwhile we also keep in mind possible applications. Our research is concentrated in several fields:





* Dusty plasmas: particles suspended in a plasma can be a nuisance or a major blessing both for applications and for fundamental research, on the earth and in space.
* EINLIGHTRED: Eindhoven Institute for Lighting Technology Research and Education.
* Environment: Pulsed corona discharges for gas and water cleaning.
* Biomedical plasmas: The healing touch of a plasma wand?
* Plasma breakdown: Starting phase of every plasma.
http://www.phys.tue.nl/EPG/

Projects

The group EPG works on various projects in low temperature plasma physics. The work can be divided in several major areas:


* Dusty Plasmas
o Polymorphous silicon solar cells
o Fundamental studies in dusty plasma interactions

* Biomedical Plasmas
o Development of Plasma Needle



* EINLIGHTRED
o New generation lamps
o Lamps in space: ARGES
o High beam quality UV lasers

* Environmental corona discharges
o Gas cleaning
o Water cleaning : YTRID project
o Corona discharges: STW-project CTF.6501
o Photo of corona discharge in nitrogen

* PolyLab
o The Polydiagnostic Laboratory

* Plasma Modeling
o PLASIMO
o Micro Discharge code

* Plasma breakdown
o Plasma Breakdown
http://www.phys.tue.nl/EPG/epghome/project.html


Dusty Plasmas
Image
In a plasma small particles get electrical charge, so they can float in the electrical fields in a plasma. The picture shows individual 10 micrometer particles floating freely. Using a laser they can be seen even by the naked eye.

Dusty plasmas have been studied in the group EPG since 1991. There are many fundamental and technological aspects related to the study of dusty plasmas. There is more background information.and an extended review.

Apart from normal plasma diagnostics a variety of diagnostics have been developed to study various particle related properties

* Charge measurement by laser induced photo detachment (paper1 , paper2)
* Particle size and density by Mie scattering (paper , Angle resolved Mie scattering during etching of an MF particle (compressed animated gif)), laser induced heating (paper1 , paper2) and ellipsometry (Thesis Swinkels)
* Particle temperature by temperature dependent fluorescence (model , thesis Swinkels)
* Composition by infrared absorption spectroscopy (paper1 , paper2) and SEM (paper)
* Particle dynamics by Laser Light scattering and video imaging (carbon particle formation), and laser Doppler methods



Apart from various items mentioned above laser induced powder formation in methane
Image
Power point presentaion 3.7 MB) and plasma formation of MoS2 powder (power point presentation 4.5 MB) have also been studied. The PhD theses of Winfred and Eva Stoffels (10 MB pdf file) as well as the thesis of Geert Swinkels (3.7 MB pdf file) are devoted to dusty plasmas.


http://www.phys.tue.nl/EPG/epghome/projects/Dustmain.htm


Great .PPT 's. Nice images and good information. 8-)
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Tue Jul 22, 2008 5:06 am

Physicists discover inorganic dust with lifelike qualities

Now, an international team has discovered that under the right conditions, particles of inorganic dust can become organised into helical structures. These structures can then interact with each other in ways that are usually associated with organic compounds and life itself.

V.N. Tsytovich of the General Physics Institute, Russian Academy of Science, in Moscow, working with colleagues there and at the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany and the University of Sydney, Australia, has studied the behaviour of complex mixtures of inorganic materials in a plasma. Plasma is essentially the fourth state of matter beyond solid, liquid and gas, in which electrons are torn from atoms leaving behind a miasma of charged particles.

Until now, physicists assumed that there could be little organisation in such a cloud of particles. However, Tsytovich and his colleagues demonstrated, using a computer model of molecular dynamics, that particles in a plasma can undergo self-organization as electronic charges become separated and the plasma becomes polarized. This effect results in microscopic strands of solid particles that twist into corkscrew shapes, or helical structures. These helical strands are themselves electronically charged and are attracted to each other.
Image
Sketch of the central part of the helical structure of the `worm' deduced from the traces left of the structure on the wall of the discharge chamber, the grains are located at the surfaces of a few cylinders inside each other [20].

Quite bizarrely, not only do these helical strands interact in a counterintuitive way in which like can attract like, but they also undergo changes that are normally associated with biological molecules, such as DNA and proteins, say the researchers. They can, for instance, divide, or bifurcate, to form two copies of the original structure. These new structures can also interact to induce changes in their neighbours and they can even evolve into yet more structures as less stable ones break down, leaving behind only the fittest structures in the plasma.

So, could helical clusters formed from interstellar dust be somehow alive? "These complex, self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter," says Tsytovich, "they are autonomous, they reproduce and they evolve".

He adds that the plasma conditions needed to form these helical structures are common in outer space. However, plasmas can also form under more down to earth conditions such as the point of a lightning strike. The researchers hint that perhaps an inorganic form of life emerged on the primordial earth, which then acted as the template for the more familiar organic molecules we know today.
http://www.eurekalert.org/pub_releases/2007-08/iop-mb081007.php


From plasma crystals and helical structures towards inorganic living matter

Abstract.

Complex plasmas may naturally self-organize themselves into stable interacting helical structures that exhibit features normally attributed to organic living matter. The self-organization is based on non-trivial physical mechanisms of plasma interactions involving over-screening of plasma polarization. As a result, each helical string composed of solid microparticles is topologically and dynamically controlled by plasma fluxes leading to particle charging and over-screening, the latter providing attraction even among helical strings of the same charge sign. These interacting complex structures exhibit thermodynamic and evolutionary features thought to be peculiar only to living matter such as bifurcations that serve as `memory marks', self-duplication, metabolic rates in a thermodynamically open system, and non-Hamiltonian dynamics. We examine the salient features of this new complex `state of soft matter' in light of the autonomy, evolution, progenity and autopoiesis principles used to define life. It is concluded that complex self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter that may exist in space provided certain conditions allow them to evolve naturally.

1. Introduction

A universal definition of life [1] relates it to autonomy and open-ended evolution [2], i.e. to autonomous systems with open-ended evolution/self-organization capacities. Thus a number of features follow: some energy transduction apparatus (to ensure energy current/flow); a permeable active boundary (membrane); two types of functionally interdependent macromolecular components (catalysts and records)—in order to articulate a `genotype–phenotype' decoupling allowing for an open-ended increase in the complexity of the individual agents (individual and `collective' evolution) [3]. The energy transduction system is necessary to `feed' the structure; the boundary as well as a property called `autopoiesis' (which is a fundamental complementarity between the structure and function [4, 5]) are necessary to sustain organized states of dissipative structures stable for a long period of time. To maintain a living organic state, it is also necessary to process nutrients into the required biochemical tools and structures through metabolism which in mathematical terms can be seen as a mapping f that transforms one metabolic configuration into another (and is invertible) f(f) = f; i.e. it is a function that acts on an instance of itself to produce another instance of itself [6, 7]. Finally, memory and reproduction of organic life are based on the properties of DNA which are negatively charged macromolecules exhibiting an important property of replication [8].

Self-organization of any structure needs energy sources and sinks in order to decrease the entropy locally. Dissipation usually serves as a sink, while external sources (such as radiation of the Sun for organic life) provide the energy input. Furthermore, memory and reproduction are necessary for a self-organizing dissipative structure to form a `living material'. The well known problem in explaining the origin of life is that the complexity of living creatures is so high that the time necessary to form the simplest organic living structure is too large compared to the age of the Earth. Similarly, the age of the Universe is also not sufficient for organic life to be created in a distant environment (similar to that on the Earth) and then transferred to the Earth.

We have performed molecular dynamics simulations to demonstrate that a random distribution of grains, interacting via the potential shown in figure 1 with a shallow attractive well |ψmin|approx10–3 and experiencing background friction and stochastic kicks, forms spherical grain crystals. In figure 2, we show results of these simulations. Application of this model is of double importance. Firstly, we resolve the problems of laboratory observations, and secondly, we predict the possible existence of large plasma poly-crystals in space—a new state of matter which is unexplored so far. Here, an important point for space applications is that the attraction potential well is shallow and therefore even weak dissipation can cause the grain capture in the well.

Physically, the attraction appears due to the electrostatic self-energy of grains, supported by plasma fluxes continuously absorbed by the grains. The fluxes are necessary to sustain the grain charges and appear almost immediately as soon as a particle is embedded in the plasma. The self-energy of grains is much larger than their kinetic and potential energies so that its (even small) changes can strongly influence grain interactions. It was first shown in [11] that for a fixed source of plasma fluxes, the electrostatic energy of two grains decreases when they approach each other. As the self-energy is supported by continuous plasma fluxes, work has to be done to maintain them and this can almost compensate the associated changes of self-energy. Nevertheless, a full compensation does not occur if the distance between the grains is large. At present it is understood [12, 13] that this phenomenon is a general feature of grain interactions in a plasma. The fluxes on grains depend on the electrostatic polarization charges of the grains and the polarization charges depend on the fluxes and create an accumulation of excess plasma charges between the grains. These plasma charges exhibit the sign opposite to that of likely charged interacting grains and therefore cause the attraction. The appearance of grain attraction is a general phenomenon which converts the grain containing matter into a new unusual state.
Image
Traces of helical structures on the walls of the chamber observed in dc cryogenic plasmas at Ti = 2.7 K. The traces of conical helical structure are shown black on the green background of discharge at several distances from the top of it; x = 0 mm—the `head' of the structure, x = 3 mm—the middle of the structure and 5 mm—the end of the structure. The whole structure looks like a `worm', hollow inside (having a dust void inside) and moving on cylindrical surfaces around the axis of discharge.

Dust structures self-organized in the plasma environment have sharp boundaries such that they are isolated from each other by regions without grains (dust voids). This effect, observed in the laboratory as well as in micro-gravity experiments onboard the ISS [14], is well explained theoretically [15, 16]. The structures and crystals should self-generate additional confining forces due to the plasma fluxes directed into the structures, i.e. these structures serve as sinks of plasmas and the ram pressure of the plasma fluxes acts on the structures to make them self-organized, self-confined and dissipative. This self-contraction should be added to the the grain pairing; their joint effect leads to formation of dust helical structures.


Image
The observed grain convection surrounding the cylindrical grain crystal. Different colors correspond to different grain velocities [18], The velocities vary from about 0.4 cm s-1 (blue) up to 1.5 cm s–1 (red). (b) The dust convection obtained in numerical simulations [19]. (c) Sketch of the model for helical structure duplication (reproduction). See details in the text.

Let us discuss some details about possible sequences of events during the reproduction. The abrupt change of the rotational angle will create an inhomogeneity in random halo dust grains surrounding the helical structure with grain charge gradient not collinear to the electric field and will create a force forming pair of toroidal vortices around the structure. For a negatively charged structure the upper toroidal vortex has a clockwise rotation while the lower has an anti-clockwise rotation. If another (second) helical structure has no bifurcation and moves close to that with bifurcation the vortices start to be created in this structure. Finally these vortices create the bifurcation in the second structure and transfer the information from the first structure to the other one.

Our analysis shows that if helical dust structures are formed in space, they can have bifurcations as memory marks and duplicate each other, and they would reveal a faster evolution rate by competing for `food' (surrounding plasma fluxes). These structures can have all necessary features to form `inorganic life'. This should be taken into account for formulation of a new SETI-like program based not only on astrophysical observations but also on planned new laboratory experiments, including those on the ISS. In the case of the success of such a program one should be faced with the possibility of resolving the low rate of evolution of organic life by investigating the possibility that the inorganic life `invents' the organic life.
http://www.iop.org/EJ/article/1367-2630/9/8/263/njp7_8_263.html
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Tue Jul 22, 2008 5:47 am

Voids and dust-density waves
Image
Major topics of our microgravity studies are related to the �void� phenomenon � the appearance of a dust-free area in the center of a weightless complex plas-ma. Of particular interest are the driving mechanisms of the void and the intensive dust density waves (see movie) which are excited at its edges. Here, video observations, profiles of basic plasma parameters measured with the probe and laser measurements of forces acting on the particles have to be combined to derive a consistent idea of the underlying physics.
http://www.ieap.uni-kiel.de/plasma/ag-piel/dlr/index_dlr.html
to movie:http://www.ieap.uni-kiel.de/plasma/ag-piel/dlr/index_dlr_dateien/wellen.mpg

Cuvette experiments and laser manipulation
Image
Using the glas tubes (cuvettes) in combination with corresponding RF-power and DC-bias on the sections of the electrodes, the ion-drag force which is mainly responsible for the �void� phenomenon can be reversed and almost homogeneous dust clouds are created in the cuvettes. Perturbations of single particles with the manipulation laser allow the exploration of the exceptional particle confinement potential.Image

http://www.ieap.uni-kiel.de/plasma/ag-piel/dlr/index_dlr.html
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Wed Jul 23, 2008 3:18 pm

Physics of charged dust particles in a plasma

Charging Mechanisms

Electrical charge accumulation on the surface of an insulating particle is the basic mechanism by which particle matter interacts with plasma. In the space environment, this charge accumulates via photoionization, secondary electron emission due to impacts with energetic particles, and collisions with the background thermal plasma. For the laboratory experiments on dusty plasmas, the principle charging mechanism will be the flux of charged particles from the plasma to dust particles residing on a plasma-exposed surface.

Particle Suspension

Assume that a spherical, macroscopic particle (grain) resides on a conducting surface exposed to a plasma. As charges pass through the sheath to the surface, they collect on the surface of the grain; in most experiments, due to the mobility of the electrons, the grain becomes negatively charged. Once the surface charge of the dust grain, QD, is large enough, the electric force (FE), due to the sheath electric field, can exceed the combination of the gravitational (mDg) and the adhesive (Fad) forces that bind the grain to the surface.

FE = QDE > Fad+ mg
ImageImage
Once released from the surface, the dust particle is accelerated through the sheath and passes into the main plasma. In laboratory conditions it is the balance between gravitational forces, electrical forces (due to electric fields within the plasma), and various neutral particle and ion drag forces that controls the transport of individual dust particles in the plasma.

Effect of a dust grain on the plasma:

Once the charged dust particles are present in the plasma, they can carry a large fraction of the negative charge of the plasma. As a result, the condition for quasi-neutrality of the plasma must be rewritten to include the effect of the dust particles.

eni - ene + QDk d(r - rk) = 0

Here, niis the ion density, neis the electron density, and the third term represents the sum of the charges carried by each of the dust particles in the plasma.

In studying the basic physics of dusty plasmas, this third term carries very interesting implications. For regions of a dusty plasma in which there are few dust particles, there can be a large excess of positive charges. The presence of the dust particles in the plasma allows the formation of electric fields within the plasma, alters the local plasma potential profile, modifies the transport of particles in the plasma, modifies certain types of ion plasma waves, and introduces new dust plasma wave modes.

Dusty plasma applications:

Because of the ubiquitous presence of particulates in plasmas, there has been a rapid rise of interest in dusty plasmas.

Plasma-material interactions -

* In plasma etching of microchips and other semiconductor devices, micron-sized debris is a common side-effect.
* This debris can (and in many cases does) redeposit on the devices causing irreparable damage.
* Such debris may also be formed at the edges of large fusion experiments due to energetic particle impacts with the plasma facing wall.

Space plasmas -

* Spacecraft interactions - Charged dust grains are common in low earth orbit and in the interplanetary medium. The presence of this charged material can cause both physical damage and electrical problems for spacecraft.
* Solar system formation - Charged dust particles in space plasmas may help to explain the formation of planetary rings, comet tails and nebulae. Because of the variety of arenas in which a dusty plasma may play a role, it is important to understand the physical properties of this plasma system.

Laboratory plasmas -

* In controlled laboratory settings, many of the phenomena of interest to both the industrial and space plasma communities can be explored.
o Collective behavior - Many experiments, including those at Auburn, are interested in measuring the properties of collective (wave) modes in dusty plasma. Much of this work is used to compare against theoretical predictions.
o Plasma (Coulomb) Crystals - Under the right conditions, the dust particles can form crystal-like 2-d and 3-d structures.
http://narn.physics.auburn.edu/research/dusty/dusty_float.html
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Re: Recovered: Dusty Plasmas

Unread postby Denis » Wed Jul 23, 2008 8:47 pm

Hi, I have a couple of questions and hope you guys don't find them to be entirely laughable. This is an issue that has bugged me for quite some time, and let me know if it doesn't even make sense. They regard the following:

arc-us wrote:One calculates the charge on an isolated dust particle in a plasma just as one would calculate the charge on a larger object—for example, an electric probe in a laboratory plasma or a satellite orbiting in the ionospheric plasma. In each case, the object is electrically floating and collects no net current from the plasma. That is,

p32equ1.jpg

Merlino_Equ1 (1)



Here's the questions:

(1) In equation 1 in the original article, couldn't the value be a 1 just as much as it is a zero, through an unconventional approach of semantics which would register a canceled out sum as a 1 as opposed to the existence of nothing?

and

(2) What could be some possible effects if that value were indeed a 1?

I doubt that this makes any scientific sense; please forgive me, I am just a layman. I am just curious.
Denis
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Sun Jul 27, 2008 8:06 am

denis wrote:Here's the questions:

(1) In equation 1 in the original article, couldn't the value be a 1 just as much as it is a zero, through an unconventional approach of semantics which would register a canceled out sum as a 1 as opposed to the existence of nothing?

and

(2) What could be some possible effects if that value were indeed a 1?

I doubt that this makes any scientific sense; please forgive me, I am just a layman. I am just curious.


StefanR
Posted: Sat Jan 05, 2008 8:38 am Post subject: static satellites Reply with quote
Modified electrical properties of sputtered thermal coatings
http://www.patentstorm.us/patents/67163 ... ption.html

Quote:
Additionally, spacecraft surfaces are exposed to space plasma environments that may create a surface electrostatic charge build-up. The charge build-up, if not controlled, may reach levels where discharges will occur that may damage spacecraft components or structure or may create deleterious electromagnetic interference of electronic components and circuitry, rendering a satellite system inoperative.

Quote:
Electrostatic discharge protection may be measured in terms of surface resistivity, also known as surface resistance. Surface resistivity (.rho.) is the resistance of a material to the flow of electrical current over the surface of a material. Consequently, a low resistivity (106 to 108 Ohms/square) is preferred in order to prevent electrostatic charge from collecting or "building up" on a surface.

Quote:
Therefore, it is highly desirable to have a thin coating with low thermophysical properties for heat control and low surface resistance for electrostatic discharge control. It is especially desirable for such a coating to be flexible and adhere to surfaces.

Quote:
Currently, the preferred method for producing and applying a very thin (t<2000 Angstroms) coating on membrane or rigid structural surfaces is through sputtering deposition. Sputter deposition, or sputtering, refers to the process of bombarding a solid (referred to as the target) with high energy ions from a plasma



Space Weather Prediction Center Topic Paper:
Satellites and Space Weather
http://www.swpc.noaa.gov/info/Satellites.html

Quote:
Types of Spacecraft Anomalies
Spacecraft anomalies are grouped into broad categories based upon the effect upon the spacecraft. A list of potential effects follows:

Surface charging*
Deep dielectric or bulk charging*
Single Event Upset (SEU) * a) Galactic cosmic rays and b) Solar proton events*
Spacecraft drag (<1000 km)*
Total dose effects*
Solar radio frequency interference and telemetry scintillation*
Debris
Spacecraft orientation*
Photonics noise*
Materials degradation
Meteorite impact
http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?p=330#p330

Stefanr
Posted: Sat Jan 05, 2008 10:30 am Post subject: dust to dust Reply with quote
Resistance or Resistivity?
http://www.ce-mag.com/archive/03/03/helpdesk.html

Quote:
Surface resistivity is defined as the ratio of the dc voltage drop per unit length to the surface current per unit width for electric current flowing across a surface.1 In effect, the surface resistivity is the resistance between two opposite sides of a square. It is independent of the size of the square (as long as the size is much greater than the film thickness) or its dimensional units. Surface resistivity is expressed in ohms per square (Ω/sq) and is traditionally used to evaluate insulative materials for electrical applications.

Surface resistance is defined as the ratio of dc voltage to the current flowing between two electrodes of a specified configuration that contact the same side of a material. This measurement is also expressed in ohms.2 It is applicable to materials regardless of construction.


Influence of carbon black in polyethylene on space chargeaccumulation
http://ieeexplore.ieee.org/Xplore/login ... 634557.pdf
Quote:
In several studies regarding space charge accumulation in peroxide crosslinked polyethylene (XLPE) it is identified that the products from the crosslinking process give rise to heterocharge accumulation in a DC-field. Several ways to reduce this accumulation have been proposed. We have studied polyethylene compounds containing 1 wt% carbon black of different types. It is found that compounds containing carbon black with very large surface area have somewhat lower accumulation of space charges in samples that are not degassed. One possibility may be increased adsorption of low molecular weight species formed at the crosslinking process. Measurements show that the addition of a low amount of carbon black gives higher resistivity but lower DC breakdown strength compared to unfilled XLPE


Plasma effects
http://www.esa.int/TEC/Space_Environmen ... LZE_0.html
Quote:
Spacecraft Charging at High Altitude

The electrostatic charging of spacecraft surfaces is the result of the spacecraft attempting to achieve a balance of currents to surfaces corresponding to an equilibrium state:

Ie+Ii+Ise+Ib+ Iph+IR=0

Here, Ie and Ii are currents of ambient electrons and ions, Ise and Ib are the secondary currents emitted by the surface as a result (secondary emission (SE), backscatter and ion-induced SE), Iph is the photoemission current and IR the bulk currents to the surface. These currents are obviously functions of the environment which is complex but can often be simplified for analysis to a Maxwellian or double-Maxwellian distribution. During geomagnetic substorms, hot plasma (10-30 keV) is introduced at geostationary orbit. The currents also depend on surface potentials and electric fields on and around the spacecraft and on the many material properties which are not always well-behaved. In the simple case where we only consider the ambient terms, Ie + Ii = 0 a surface floats at 2 to 3 times the electron temperature (in Volts). This results from the higher current of more mobile electrons, requiring a high negative surface charge to repel them. However, the modifying factors can be very important in space.

The important material properties are:

Dielectric thickness;
Dielectric constant;
Dielectric resistivity - this is not generally a constant in space but is illumination, temperature, radiation and field-dependent;
Surface resistivity;
Secondary electron emission yield as a function of incident electron or ion energy;
Photoemission current (from solar illumination).



HIGH VOLUME & SURFACE RESISTIVITY ,INSULATION RESISTANCE
http://www.electricinsulations.com/hvs.htm
Quote:
Insulating material are used to isolate the live electric parts i.e. which are at an elevated electric potential. Ideally, the insulating material should be totally non-conductive i.e. the resistivity should be infinity. However, materials employed in practice do carry a certain, usually very weak current (leakage current) when a direct voltage is applied. Thus the resistivity of electrical insulating material is finite, although of extremely high value. The higher is the resistivity of the material, the better is its quality.

The leakage current passing through the insulated portion at a stable process of conduction i.e. a sufficiently long time after a direct voltage is applied, is also constant and is known as residual current. The resistance R in of an insulation equals to the ratio of direct voltage V applied to this insulation to the residual current Im passing through the portion i.e. R in =V / I in Ohms.

The total current passing through the insulation may be considered as consisting of two components of current - one which flow through the volume of insulation Iv, and the other passing over the surface of insulation Is. Unlike conduction current in metals, this component currents through volume and surface, in case of insulating materials has special significance. Hence the resistance is looked upon differently corresponding to volume and surface leakage current. Resistance which is obtained by the ratio of applied voltage V to volume leakage current Iv is known as volume resistance and that due to surface leakage current Is is known as surface resistance. The volume and surface resistance as obtained are dependent on the electrode geometry and physical dimension of the insulating material under test. Hence to define the basic insulation properties, the following two quantities are used - (i) Volume Resistivity (ii) Surface resistivity.
http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?p=333#p333


Well Denis, I'm no expert too so don't take my word. Above is some information which is from the Comet Holmes thread.
Altough it more pertains to satellites but it can give some extra insight into the question that you pose.
The reason why they put a zero value at the eqaution you mention is that they are trying to calculate the charge of a floating particle. And as it is floating the net total of forces acting on the particle is zero. If it would be otherwise it wouldn't be floating anymore, but it will be drifting.
Charging the dust

One calculates the charge on an isolated dust particle in a plasma just as one would calculate the charge on a larger object—for example, an electric probe in a laboratory plasma or a satellite orbiting in the ionospheric plasma. In each case, the object is electrically floating and collects no net current from the plasma. That is,

Image
p32equ1.jpg (1.45 KB) Viewed 472 times

Merlino_Equ1 (1)

where Iα represents the possible currents to the particle. The various contributions come from electron and ion currents, secondary electron emission, thermionic emission, and photoelectron emission.6


And as stated in the qoute above
The electrostatic charging of spacecraft surfaces is the result of the spacecraft attempting to achieve a balance of currents to surfaces corresponding to an equilibrium state:

Ie+Ii+Ise+Ib+ Iph+IR=0

Here, Ie and Ii are currents of ambient electrons and ions, Ise and Ib are the secondary currents emitted by the surface as a result (secondary emission (SE), backscatter and ion-induced SE), Iph is the photoemission current and IR the bulk currents to the surface.


But these are for dust and satellites attempts to a equilibrium state with the environment wherein it resides, that's why the first article in this thread also states:
Image
In ordinary electron−ion plasmas without dust, the charge on the ions generally remains fixed, even in plasmas containing negative ions. But in a dusty plasma, the charge on a particle does not stay fixed. Because the charge depends on the particle's surface potential relative to the plasma potential, fluctuations in the plasma potential brought about, for example, by plasma waves can cause the dust charge to vary. The charge also varies stochastically, as individual electrons and ions are absorbed at random times. For nanometer particles, this effect can actually switch the charge's sign. Such alternation can enhance the growth rate of particles by collision or coagulation in the dusty plasmas of semiconductor manufacturing reactors and prestellar nebulae.

or
Particle Suspension

Assume that a spherical, macroscopic particle (grain) resides on a conducting surface exposed to a plasma. As charges pass through the sheath to the surface, they collect on the surface of the grain; in most experiments, due to the mobility of the electrons, the grain becomes negatively charged. Once the surface charge of the dust grain, QD, is large enough, the electric force (FE), due to the sheath electric field, can exceed the combination of the gravitational (mDg) and the adhesive (Fad) forces that bind the grain to the surface.

FE = QDE > Fad+ mg



And the dust will have it's effect on the behaviour of the plasma:

Effect of a dust grain on the plasma:

Once the charged dust particles are present in the plasma, they can carry a large fraction of the negative charge of the plasma. As a result, the condition for quasi-neutrality of the plasma must be rewritten to include the effect of the dust particles.

eni - ene + QDk d(r - rk) = 0

Here, niis the ion density, neis the electron density, and the third term represents the sum of the charges carried by each of the dust particles in the plasma.

In studying the basic physics of dusty plasmas, this third term carries very interesting implications. For regions of a dusty plasma in which there are few dust particles, there can be a large excess of positive charges. The presence of the dust particles in the plasma allows the formation of electric fields within the plasma, alters the local plasma potential profile, modifies the transport of particles in the plasma, modifies certain types of ion plasma waves, and introduces new dust plasma wave modes.


Hope this helps a little. :)
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Dusty Crystal Plasma

Unread postby StefanR » Wed Nov 12, 2008 4:17 pm

Image
Shock waves around dusty, young stars might be creating the raw materials for planets, according to new observations from NASA's Spitzer Space Telescope.

The evidence comes in the form of tiny crystals. Spitzer detected crystals similar in make-up to quartz around young stars just beginning to form planets. The crystals, called cristobalite and tridymite, are known to reside in comets, in volcanic lava flows on Earth, and in some meteorites that land on Earth.
When Forrest and his colleagues used Spitzer to examine five young planet-forming disks about 400 light-years away, they detected the signature of silica crystals. Silica is made of only silicon and oxygen and is the main ingredient in glass. When melted and crystallized, it can make the large hexagonal quartz crystals often sold as mystical tokens. When heated to even higher temperatures, it can also form small crystals like those commonly found around volcanoes.
It is this high-temperature form of silica crystals, specifically cristobalite and tridymite, that Forrest's team found in planet-forming disks around other stars for the first time. "Cristobalite and tridymite are essentially high-temperature forms of quartz," said Sargent. "If you heat quartz crystals, you'll get these compounds."
In fact, the crystals require temperatures as high as 1,220 Kelvin (about 1,740 degrees Fahrenheit) to form. But young planet-forming disks are only about 100 to 1,000 Kelvin (about minus 280 degrees Fahrenheit to 1,340 Fahrenheit) -- too cold to make the crystals. Because the crystals require heating followed by rapid cooling to form, astronomers theorized that shock waves could be the cause.(leaving out...)
Shock waves, or supersonic waves of pressure, are thought to be created in planet-forming disks when clouds of gas swirling around at high speeds collide. Some theorists think that shock waves might also accompany the formation of giant planets.
The findings are in agreement with local evidence from our own solar system. Spherical pebbles, called chondrules, found in ancient meteorites that fell to Earth are also thought to have been crystallized by shock waves in our solar system's young planet-forming disk. In addition, NASA's Stardust mission found tridymite minerals in comet Wild 2.

http://www.spitzer.caltech.edu/Media/releases/ssc2008-20/release.shtml

It would definitely be too inhuman to elektrocute these guys, but it might just do the trick of getting them to wake up for a second. :twisted:
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Re: Recovered: Dusty Plasmas

Unread postby junglelord » Wed Nov 12, 2008 4:38 pm

That is one beautiful Octahedron (Platonic Solid-Sacred Geometry).
Very cool that quartz is essential. I am fixated with quartz myself.
:D
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Wed Nov 12, 2008 5:04 pm

And let's not forget the coulomb crystal

Image
Negatively-charged dust particles in plasmas can form crystal-like structures. Mitsuhiro Nambu, Sergey Vladimirov and Osamu Ishihara have suggested that the mechanism by which this occurs may be analogous to the effect which produces superconductivity.

Plasmas are essentially gases in which the constituent particles are electrically charged. Each particle is either positive or negative according to whether it has an excess of protons (+) or electrons (-). In high-temperature plasmas, such as in a fluorescent light tube or in the region around a star, most of the particles are simple, consisting of single electrons and positively charged atomic nuclei. However in recent years a great deal of interest has developed in so-called ``dusty plasmas''. These are low-temperature plasmas that contain highly charged particulates which may be as large as a micron (a thousandth of a mm) across.

Recent experiments have revealed that the particulates embedded in plasmas have an intriguing tendency to form crystalline structures - i.e. regular, repeating arrangements of particulates. The formation of these structures has been difficult to explain because the electrostatic forces between the negatively-charged dust particles themselves are repulsive, since particles with the same sense of electric charge repel one another. Prof. Mitsuhiro Nambu (Kyushu University; currently at Tokyo Metropolitan Institute of Technology), Sergey Vladimirov and Prof. Osamu Ishihara (Texas Tech University; currently at Yokohama University) have suggested that the explanation may lie in collective effects, where large numbers of the particles act in a coherent manner, between the dusty particles and the flow of positively charged ions through the static crystalline structure towards the negatively charged electrode near which the crystalline structure forms. These effects are analogous to the formation of so-called ``Cooper pairs'' of electrons that give rise to superconductivity, and this theory explains the formation of both square and hexagonal crystals, as observed experimentally

http://www.physics.usyd.edu.au/~vladimi/projects/cryst.html
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Re: Recovered: Dusty Plasmas

Unread postby StefanR » Sat Feb 07, 2009 1:51 pm

cosmic dust fountain

Space dust annoys astronomers just as much as the household variety when it interferes with their observations of distant stars. And yet space dust also poses one of the great mysteries of astronomy.
"We not only do not know what the stuff is, but we do not know where it is made or how it gets into space," said Donald York, the Horace B. Horton Professor in Astronomy and Astrophysics at the University of Chicago.

Dust in the solar wind
During this transition, which takes place over tens of thousands of years, these stars lose an outer layer of their atmosphere. Dust may form in this cooling layer, which radiation pressure coming from the star's interior pushes out the dust away from the star, along with a fair amount of gas.
In double-star systems, a disk of material from the post-AGB star may form around the second smaller, more slowly evolving star. "When disks form in astronomy, they often form jets that blow part of the material out of the original system, distributing the material in space," York explained.

This seems to be the phenomenon that Witt's team observed in the Red Rectangle, probably the best example so far discovered

"If a cloud of gas and dust collapses under its own gravity, it immediately gets hotter and starts to evaporate," York said. Something, possibly dust, must immediately cool the cloud to prevent it from reheating.
The giant star sitting in the Red Rectangle is among those that are far too hot to allow dust condensation within their atmospheres. And yet a giant ring of dusty gas encircles it.Some of this material ends up in a disk of accumulating dust that surrounds that smaller companion star. Gradually, over a period of approximately 500 years, the material spirals into the smaller star.

Bipolar behavior
Just before this happens, the smaller star ejects a small fraction of the accumulated matter in opposite directions via two gaseous jets, called "bipolar jets."

Cosmic dust production has eluded telescopic detection because it only lasts for perhaps 10,000 years—a brief period in the lifetime of a star.

The Red Rectangle displays several phenomena that require far-ultraviolet radiation as a power source. "The trouble is that the very luminous central star in the Red Rectangle is not hot enough to produce the required UV radiation," Witt said, so he and his colleagues set out to find it.
It turned out neither star in the binary system is the source of the UV radiation, but rather the hot, inner region of the disk swirling around the secondary, which reaches temperatures near 20,000 degrees. Their observations, Witt said, "have been greatly more productive than we could have imagined in our wildest dreams."
http://news.uchicago.edu/news.php?asset_id=1537

And wild their dreams most surely are. :? Dusty gas. :idea:
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Re: Recovered: Dusty Plasmas

Unread postby Grey Cloud » Sat Feb 07, 2009 4:40 pm

I've just read the article at Chicago uni and it is a great example of modern writing, i.e. writing which you are supposed to read and accept but not think upon.

"We not only do not know what the stuff is, but we do not know where it is made or how it gets into space," said Donald York, the Horace B. Horton Professor in Astronomy and Astrophysics at the University of Chicago.
At this point they are fairly clueless.
But now York, the University of Toledo's Adolf Witt and their collaborators have observed a double-star system that displays all the characteristics that astronomers suspect are associated with dust production.
But they have one or two ideas. Note the term 'associated with'. Associated with is not synonymous with cause of.

One of the double stars is of a type that astronomers regard as a likely sourceof dust.
Still fairly uncertain here but they have another idea.

During this transition, which takes place over tens of thousands of years, these stars lose an outer layer of their atmosphere. Dust may form in this cooling layer, which radiation pressure coming from the star's interior pushes out the dust away from the star, along with a fair amount of gas.
Suddenly they know how long the process takes (Holy leap of faith, Batman!).
May. So much for the exact sciences.
'A fair amount' is a scientific term which is greater than a slack handful but smaller than a shed full.
Notice that the dust has appeared miraculously as no mechanism has been suggested other than it 'may' form in this layer. The dust is not formed from the gas.

In double-star systems, a disk of material from the post-AGB star may formaround the second smaller, more slowly evolving star. "When disks form in astronomy, they often formjets that blow part of the material out of the original system, distributing the material in space," York explained.
The word 'may' again.
'When disks form in astronomy' - as opposed to real life?
'They often form' - exact science again.

This seems to be the phenomenon that Witt's team observed in the Red Rectangle, probably the best example so far discovered. The discovery has wide-ranging implications, because dust is critical to scientific theories about how stars form.
Perhaps it could be that they may possibly be not quite as certain as they would have you believe.
Dust may well be critical to how stars form but they are talking about the formation of dust from already formed stars.

"If a cloud of gas and dust collapses under its own gravity, it immediately gets hotter and starts to evaporate," York said. Something, possibly dust, must immediately cool the cloud to prevent it from reheating.
Eh? Do gas and dust have their own gravity? How can something 'immediately' get hotter and start to evaporate and simultaneously 'immediately' cool? Personally I would have thought that dust was more likely to trap the heat.

The giant star sitting in the Red Rectangle is among those that are far too hot to allow dust condensation within their atmospheres. And yet a giant ring of dusty gas encircles it.
Once more the Universe proves that it knows nothing about science. N.B. Dusty gas is not to be confused with gassy dust.

Witt's team made approximately 15 hoursof observations on the double star over a seven-year period
Hardly 'round the clock surveillance' is it?
"Our observations have shown that it is most likelythe gravitational or tidal interaction between our Red Rectangle giant star and a close sun-like companion star that causes material to leave the envelope of the giant," said Witt, an emeritus distinguished university professor of astronomy.
Where did the 'gravitational or tidal interaction' thing come from, this is the first mention of it. Also, above it stated that jets form and blow the material into space. To me this is entirely different to it being pulled up by the other, smaller, star.
And surely he should be a distinguished emeritus yada, rather than an emeritus distinguished?

Some of this material ends up in a disk of accumulating dust that surrounds that smaller companion star. Gradually, over a period of approximately 500 years, the material spirals into the smaller star.
So according to the beginning of the article, it takes 'tens of thousands of years' to lose an outer layer of its atmosphere but it takes aproximately 500 years to get from the ring 'into' the smaller star.
The Universe may not know anything about science but it always seems to work in round figures.
Just before this happens, the smaller star ejects a small fraction of the accumulated matter in opposite directions via two gaseous jets, called "bipolar jets."
Eh? Does it spiral into the smaller star or not? How do these jets fit in with the gravitational or tidal interactions?

Other quantities of the matter pulled from the envelope of the giant end up in a disk that skirts both stars, where it cools.
So now we have gone from gas and dust, to dusty gas, to matter. We now have it cooling but still do not have the mechanism for the cooling.
The Universe is pulling matter from envelopes and the scientists are pulling theories from hats.
"The heavy elements like iron, nickel, silicon, calcium and carbon condense out into solid grains..."
As opposed to liquid or gasous grains (which they are probably saving for another theory).

Cosmic dust production has eluded telescopic detection because it only lasts for perhaps 10,000 years—a brief period in the lifetime of a star. Astronomers have observed other objects similar to the Red Rectangle in Earth's neighborhood of the Milky Way. This suggests that the process Witt's team has observed is quite common when viewed over the lifetime of the galaxy.
So which is it - tens of thousands of years or perhaps ten thousand years?
Viewed over the lifetime of the galaxy, as opposed to 15 hours over seven years.
"Processes very similar to what we are observing in the Red Rectangle nebula have happened maybe hundreds of millions of times since the formation of the Milky Way," said Witt,
That would be pure speculation then, would it?

Their observations, Witt said, "have been greatly more productive than we could have imagined in our wildest dreams."
The University of Chicago - where dreams come true.
Adolf Witt - know to his friends as (h)Alf Witt.
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Re: Recovered: Dusty Plasmas

Unread postby Grey Cloud » Sat Feb 07, 2009 4:59 pm

Cheers Stefan.
I forgot all about Match of the Day :x I managed to catch the last part of the last game, a nil - nil bore draw. :cry:
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Re: Recovered: Dusty Plasmas

Unread postby bboyer » Sat Feb 07, 2009 6:22 pm

Since the last crash of the forum and resulting corruption of many of the old postings' photo and illustration attachments, here's a link to a pdf of the first post in this thread that has all the photos (the post's original html link doesn't have them any longer either, for whatever reason). Those interested may want to download the pdf for their personal reference (content is protected from copying etc, but may be printed) while it's still available, otherwise you have to purchase it from the original download source (Physics Today).

http://dusty.physics.uiowa.edu/~goree/p ... -06-04.pdf
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