Whistler waves, double layers, magnetic reconnection

[seasmith]

~
As the phrase "flux transfer events" is used above in the description of "...the establishment of a linkage between the Earth's field and the IMF (Interplanetary Magnetic Field)..."
and refers to a "finite rate of flux reconnection"
while further stating that "It may be loosely defined as a flow of plasma..."
it would appear that the the definition Is being given; as un-clearly as pedantically possible.

Then, just to thicken the fog of flux, they become hopelessly mired in ye old 'Particle-Wave dichotomy', because
they cannot say what it Is that's fluxing.

[junglelord]

Terminology in cosmology gets a failing grade.


My pet peeve is "SOLAR WIND"


O really wind in space? Can anyone hear me scream?


I think "SOLAR CURRENT" is the only appropriate term...wind indeed, a lot of hot air for sure.

[StefanR]

Yes indeed the language does sometimes seem to be a problem.
On the other hand some experiments and space observations are being made and that is where the gold is in my opinion.
So the problem lies in translating it correctly in the right terms.

I still have some tabs in my browser about double layers which seem to be interesting especially in relation with the pdf Michael pointed out.

(Double Layers and Circuits in Astrophysics; Hannes Alfvén)
http://ntrs.nasa.gov/archive/nasa/casi. ... 013880.pdf

This is a very nice read and also pretty significant in my opinion, this double layer stuff.

[StefanR]

Accumulators must be charged slowly to avoid damage. But vehicles, in particular, are associated with many applications that need a fast charging capability—for example, when braking energy is harnessed in cars or streetcars. With this in mind, Siemens is promoting the use of double layer capacitors, or so-called supercaps—devices that store electrical energy by separating the charges as soon as a voltage is applied. Supercaps offer capacitances of 300 to 10,000 F. Charge separation takes place at the boundary layer between a solid body and a liquid. High capacitances are achieved by ensuring that the charges are separated by a distance of only atomic dimensions, and by the use of porous graphite electrodes with a large specific surface area.

Supercaps have low energy densities—3 to 5 Wh/kg—but extremely high power densities of 2,000 to 10,000 W/kg. They can be charged within a few seconds, and at a million or so charge-discharge cycles, their service life is extremely long. This is due to the fact that the charge separation processes occurring within them are purely physical in nature. They can take up and release large quantities of energy extremely quickly. This makes it possible to use an electric motor in a hybrid vehicle, streetcar, or locomotive as a generator that recovers braking energy. This regenerated energy is stored in supercaps and re-used when the vehicle accelerates again. The resulting advantage is fuel and energy savings of between five and 25 %, depending on the driving cycle. The capacitor packs can either be carried in the vehicle itself or permanently built into segments of subway lines.

Accumulators such as lead-acid, nickel-metal hydride and lithium-ion batteries have a service life of between three and ten years, on average. They function on electrochemical principles. Charging the battery converts electrical energy into chemical energy. When an electrical device is connected, chemical energy is converted back into electrical energy. Energy stores such as double layer capacitors, in contrast, store energy electrostatically. They last almost indefinitely and exhibit high power densities. However, their energy densities are low. For this reason, their primary use is to cover peak loads such as engine starts or acceleration in hybrid applications.

http://w1.siemens.com/innovation/en/pub ... torage.htm

[StefanR]

Late-time diagnostics from a 2-D reduced Vlasov simulation with strongly magnetized electron and unmagnetized ions showing the parallel electric field (top) and mean parallel electron drift (bottom). The double layer is the curved structure in the middle of the simulation domain. The electron holes are associated with the biploar (red/blue) pairs in the parallel electric field (top frame).

The Space Plasma Group at the University of Colorado studies the nonlinear evolution of space and laboratory plasmas driven by electric currents and beams of energetic particles. Recent investigations have employed numerical simulations and analytical modeling to understand the origins and properties of coherent nonlinear structures (most notably double layers and electron phase-space holes, as shown in the accompanying image from one of our 2-D simulations). Such structures have been observed in Earth's auroral zone, as well as in other space-plasma and laboratory environments.

http://cips.colorado.edu/spaceplasma/

[StefanR]

Electric double layers (DLs) occur naturally in a variety of space plasma environments
(aurorae, solar wind, extragalactic jets...) and are being characterized using satellites. The
potential drop that they can sustain over a narrow region can energise charged particles.
Terrestrial laboratory experiments have been successfully demonstrated for decades in the
case of current-driven DLs and more recently of current-free (but driven by an applied
potential) propagating or stationary DLs. Current-driven DLs generated by a constriction in a
gas-discharge tube or by plasma expansion in a diverging magnetic field are well
documented. A current-free electric double layer has been recently found in a laboratory
plasma expanding in a divergent magnetic field. The experiment simply consists of a
radiofrequency helicon plasma source attached to a diffusion chamber. Two solenoids placed
around the source tube create a diverging magnetic field near the exit of the source and a DL
can self consistently form in this physical and magnetic nozzle. The double layer is
characterized using a retarding field energy analyzer which can be moved along the main axis
of expansion or across the expansion area. The DL potential drop and thickness are typically
about 3kTe and 50 debye lengths in argon, respectively, and the ion beam generated
downstream is supersonic (twice the sound speed). The ion beam is detected from the centre
out to a radius corresponding to the plasma source tube and is not greatly affected by the
expanding magnetic field. The wall charging of the insulating helicon source (glass tube)
allows the presence of large plasma potentials upstream of the DL (up to 100 V). The DL can
be self consistently created for a variety of gases (argon, hydrogen, oxygen, xenon...), is
formed during the plasma breakdown and is stable thereafter (at about 100 microseconds).
The beam density and energy strongly depend on the gas pressure, the magnetic field
configuration and the system geometry. Tests have also been performed over a large range of
pumping speeds to get some insight into possible applications of this DL to space plasmas.
Although a similar DL has been recently observed in various helicon systems worldwide,
there is no theory available in the literature. Preliminary results on analytical modelling of
some aspects of this current-free double layer will be presented.

http://www.phys.uit.no/IPELS05/Abstract ... 2005IT.pdf

[StefanR]

Helicon reactor in operation

ESA has confirmed the principle of a new space thruster that may ultimately give much more thrust than today’s electric propulsion techniques. The concept is an ingenious one, inspired by the northern and southern aurorae, the glows in the sky that signal increased solar activity.

“Essentially the concept exploits a natural phenomenon we see taking place in space,” says Dr Roger Walker of ESA’s Advanced Concepts Team. "When the solar wind, a ‘plasma’ of electrified gas released by the Sun, hits the magnetic field of the Earth, it creates a boundary consisting of two plasma layers. Each layer has differing electrical properties and this can accelerate some particles of the solar wind across the boundary, causing them to collide with the Earth’s atmosphere and create the aurora."

In essence, a plasma double layer is the electrostatic equivalent of a waterfall. Just as water molecules pick up energy as they fall between the two different heights, so electrically charged particles pick up energy as they travel through the layers of different electrical properties.

Researchers Christine Charles and Rod Boswell at the Australian National University in Canberra, first created plasma double layers in their laboratory in 2003 and realised their accelerating properties could enable new spacecraft thrusters. This led the group to develop a prototype called the Helicon Double Layer Thruster.
......
To create the double layer, Chabert and colleagues created a hollow tube around which was wound a radio antenna. Argon gas was continuously pumped into the tube and the antenna transmitted helicoidal radio waves of 13 megahertz. This ionised the argon creating a plasma. A diverging magnetic field at the end of the tube then forced the plasma leaving the pipe to expand. This allowed two different plasmas to be formed, upstream within the tube and downstream, and so the double layer was created at their boundary. This accelerated further argon plasma from the tube into a supersonic beam, creating thrust.

http://www.esa.int/esaCP/SEM6HSVLWFE_index_0.html

[StefanR]

Abstract
This thesis reports theoretical and experimental studies of three distinct types of double-layers. First, we describe the space-charge double-layer that forms between two plasmas with different densities and thermal energies. Three progressively more realistic models are treated by fluid theory, taking into account four species of particles: electrons and ions reflected by the double-layer, and electrons and ions transmitted through it. Initially, the two plasmas are assumed to be cold, and the self-consistent potential, electric field and space-charge distributions within the double-layer are determined. Subsequently, the effects of thermal velocities are taken into account for the reflected particles, and the modifications to the cold plasma solutions are established. Finally, the further modifications due to thermal velocities of the transmitted particles are examined. The applicability of a one-dimensional fluid description, rather than plasma kinetic theory, is discussed. One valuable product of this description is the potential difference across the double-layer in terms of the parameters of the two plasmas which it separates. A useful length parameter is defined characterizing the distance over which most of this potential is dropped. Comparisons are then made between theoretical predictions, and double-layer potentials and lengths deduced from laboratory and space plasma experiments. In our second double-layer study, Langmuir probe measurements have been carried out which confirm the occurrence of double-layers in an argon positive column. Pulsing the discharge current permits probe measurements to be performed in the presence of the double-layer. Supplementary evidence, obtained from DC and pulsed discharges, indicates that the double-layers formed in the two modes of operation are similar. The double-layers observed are weak and stable; their relation to other classes of double-layers are discussed, and directions for future work are suggested. Finally, we analyze the double-layer that forms due to ponderomotive effects produced by a convectively amplifying electron beam-plasma interaction. Our model takes account of finite plasma electron temperature and electron-neutral collison frequency. A double-layer forms in the region where the instability saturates. We describe our experiment to observe this double-layer, using an electron beam probe to measure the DC and RF electric fields. In order to interpret the measurements, we have extended the theory of this diagnostic technique to include nonlinear effects. The double-layer electric field was predicted to be at the detection limits of the experiment, and was found to be masked by background fields and scatter in the data.

http://adsabs.harvard.edu/abs/1981PhDT........83L

[StefanR]

What is Zeta Potential?

Back

Zeta potential is the charge that develops at the interface between a solid surface and its liquid medium. This potential, which is measured in MilliVolts, may arise by any of several mechanisms. Among these are the dissociation of ionogenic groups in the particle surface and the differential adsorption of solution ions into the surface region. The net charge at the particle surface affects the ion distribution in the nearby region, increasing the concentration of counterions close to the surface. Thus, an electrical double layer is formed in the region of the particle-liquid interface.

Fig. 1 What is Zeta Potential?

This double layer (upper part of figure) consists of two parts: an inner region that includes ions bound relatively tightly to the surface, and an outer region where a balance of electrostatic forces and random thermal motion determines the ion distribution. The potential in this region, therefore, decays with increasing distance from the surface until, at sufficient distance, it reaches the bulk solution value, conventionally taken to be zero. This decay is shown by the lower part of the figure and the indication is given that the zeta potential is the value at the surface of shear.

In an electric field, as in microelectrophoresis, each particle and its most closely associated ions move through the solution as a unit, and the potential at the surface of shear between this unit and the surrounding medium is known as the zeta potential. When a layer of macromolecules is adsorbed on the particle's surface, it shifts the shear plane further from the surface and alters the zeta potential.

Zeta potential is therefore a function of the surface charge of the particle, any adsorbed layer at the interface, and the nature and composition of the surrounding suspension medium. It can be experimentally determined and, because it reflects the effective charge on the particles and is therefore related to the electrostatic repulsion between them, the zeta potential has proven to be extremely relevant to the practical study and control of colloidal stability and flocculation processes.

http://www.bic.com/WhatisZetaPotential.html

[StefanR]

Electrical Double Layer

The figure below illustrates schematically the electrical double layer. A plane of charge due to complexation or dissociation exists on a surface. For example, consider in this case that the total charge is negative as shown in the figure below. It may also be the case that ions from solution are specifically absorbed, as shown by the negatively charged green species. Counterions attracted to the surface by electrostatics shield the surface charge. The counterions are not all in the same plane, however, because they are held in a dynamic balance by electrostatic attraction and the tendency to diffuse away. The concentration of ions in the diffuse layer decays with distance from the surface. Thus the surface charge forms one layer and the diffuse shielding charge forms the other layer, hence the term “double layer”.

The double layer has a certain structure. The Inner Helmholtz Plane (IHP) is the plane cutting through the center of the adsorbed species. The Outer Helmholtz plane (OHP) is the plane cutting through the positive ions at their position of closest approach. Ions in the diffuse layer are always being exchanged at the surface, but the surface excess of counterions always exactly balances the total charge associated with the solid. The Gouy-Chapman theory describes the physics of the diffuse part of the double layer. One solves Poisson’s equation where the charge density is given by the Boltzmann distribution of charge in the diffuse layer. Many basic texts in physical chemistry and colloid science discuss details of the double layer.

http://www.andrew.cmu.edu/course/39-801 ... theory.htm

[FS3]

Just came over a good description from the Finnish University:

Nice pictogrames, good reasoning - and finally something which is more or less the description of a dissolving double layer - copyright Alfvén...

....This means that magnetic field lines are electric equipotentials...

...Consider the motion of low-energy plasma in the plasma sheet...

...ring currents around earth...

...The cause of reconnection may be external (driven reconnection)
or some plasma instability (spontaneous reconnection)...

...

FS3

[StefanR]

Highlights from Cluster-THEMIS workshop

17 Oct 2008
Nearly 120 space scientists from around the world participated in the First Joint Cluster-THEMIS workshop held at the University of New Hampshire (Durham, USA) from 23 to 26 September 2008. The purpose of the meeting was to discuss recent results obtained by these two missions and to foster cooperation.

Cluster is an ESA mission launched in 2000 and consisting of four identical spacecraft flying in a polar orbit. THEMIS is a NASA mission launched in 2007 with five identical spacecraft flying in an equatorial orbit. This constellation of nine spacecraft enables researchers to study, in an unprecedented way, major physical processes taking place in the environment of Earth including: collisionless shock formation and evolution, magnetic reconnection, solar wind particle entry into the Earth's magnetosphere and particle acceleration during geomagnetic substorms.

The four-day workshop was organized in a number of plenary sessions during which the participants discussed new results from both missions. Highlights from the plenary sessions can be accessed via the links below:

-Solar wind, bow shock and magnetopause
-Magnetopause, polar cusp, transients and FTEs
-Magnetotail and substorms
-Inner Magnetosphere

http://sci.esa.int/science-e/www/object ... ctid=43567

Nice pdf's with a mix of observations and theory. Might be an idea to flesh out the observations....later maybe.

[FS3]

What researchers at the University of California, Los Angeles, are calling a "mystery" - could present no puzzle at all for those scientists who know about plasma, electricity and...

...double layers!

As indeed it sounds like the description of an unloading double layer or capacitor when that simply peeling of an ordinary sticky tape in a vacuum can generate X-rays and an - obviousely - flow of currents, similar to the well known discharging of a capacitor. "What's causing the transfer of charge, of electrons or protons, what the accepting and donor groups are — these things were said to be much less clear."

Some static electricity may build up on the surfaces of the tape through induced charge seperation while either the tape itself or the thin layer of glue may act as a insulating dielelectricum.

From:
http://www.nature.com/news/2008/081022/ ... .1185.html

Sticky tape generates X-rays
How weird is that?
Katharine Sanderson

Christmas could bring with it a new hazard as you wrap your gifts – X-ray-emitting sticky tape.

Researchers at the University of California, Los Angeles, have shown that simply peeling ordinary sticky tape in a vacuum can generate enough X-rays to take an image — of one of the scientists' own fingers (see videos).

"At some point we were a little bit scared," says Juan Escobar, a member of the research team. But he and his co-workers soon realized that the X-rays were only emitted when the kit was used in a vacuum. "We don't want to scare people from using Scotch tape in everyday life," Escobar adds.

This kind of energy release — known as triboluminescence and seen in the form of light — occurs whenever a solid (often a crystal) is crushed, rubbed or scratched. It is a long-known, if somewhat mysterious, phenomenon, seen by Francis Bacon in 1605. He noticed that scratching a lump of sugar caused it to give off light.

The leading explanation posits that when a crystal is crushed or split, the process separates opposite charges. When these charges are neutralized, they release a burst of energy in the form of light.

As long ago as 1953, a team of scientists based in Russia suggested that peeling sticky tape produced X-rays. But "we were very sceptical about the old results," says Escobar. His team decided to look into the phenomenon anyway, and found that X-rays were indeed given off, in high-energy pulses.

When the researchers placed a small plastic window in their vacuum chamber, they were even able to take an X-ray image of a finger, using a dental X-ray detector....

Isn´t this fascinating?

FS3

[StefanR]

Collisions between clusters of galaxies should produce shockwaves whose magnetic fields can boost loose protons and electrons up to very high energies, but until now there was no clear evidence of it happening.

Now, researchers led by Reinout van Weeren of Leiden University in the Netherlands have used radio telescopes in the Netherlands, India and the US to image a huge bright arc at the interface of two colliding galaxy clusters, known collectively as CIZA J2242.8+5301. The energy spectrum of the radio waves changes across the arc in a way that fits models of shock acceleration.

The shockwave stretches for more than 6 million light years, and van Weeren calculates that it could easily accelerate protons to energies of up to 1019 eV. That is millions of times as high as the particles in any atom smasher and in the energy range of mysterious charged particles called ultra-high energy cosmic rays that occasionally hit Earth's atmosphere.

http://www.newscientist.com/article/dn1 ... -rays.html

This is a composite image of the northern part of the galaxy cluster Abell 1758, located about 3.2 billion light years from Earth, showing the effects of a collision between two smaller galaxy clusters. Chandra X-ray data (blue) reveals hot gas in the cluster and data from the Giant Metrewave Radio Telescope (GMRT) in India (pink) shows huge "halos" generated by ultra-relativistic particles and magnetic fields over vast scales. Optical data from the Digitized Sky Survey are colored gold.

A study of this galaxy cluster and 31 others with Chandra and the GMRT shows that huge radio halos are generated during collisions between galaxy clusters. This result implies that galaxy clusters with radio halos are still forming, while clusters without this radio emission are not still accumulating large amounts of material. The result also implies that relativistic electrons are likely accelerated by turbulence generated by mergers between clusters.

http://chandra.harvard.edu/photo/2010/a1758/

[seasmith]

StefanR wrote:

ultra-relativistic particles and magnetic fields over vast scales.

http://www.newscientist.com/article/dn1 ... -rays.html

Although the NewScientist article is all about collisions and shock waves, there is a remarkable semblance [on a range of scale down] with this latest image from spaceweather.com :



The usual vast twisting and twining of magnetic DL boundaries
coralling and conducing radiant (at relativistic speeds)
currents of electrons, posi-ions and ENA's, from cell>to<cell, of plasmic matter.


As in the " Giant Ribbon Discovered..." in a concurrent thread, it is most likely
Magnetic Flux (being more fluid) which precedes the transmission of Charged and neutral ' particles '.
http://www.thunderbolts.info/wp/forum/phpB ... &start=105

imo