Problems With Magnetic Reconnection

[michaelsuede]

I have no idea how MM thinks that the particles will magically gain energy without magnetic reconnection (it cannot be induction - see above)

They gain energy by ramping across a DL and the plasma gets it kinetic energy from the particles impinging on the anode and cathode side of the DL.

Given that differing plasmas will create a double layer, this seems like the only logical conclusion as to the explaination of magnetic reconnection.

Let us not forget that MHD theory is incapable of describing the mechanics of a DL and therefore neglects the DL as the cause of magnetic reconnection.

When your models are predicated on junk science, it is unsurprising that the theories concluded from those models will also be junk science.

 

[Cuddles]

As usual, stop with the personal attacks and bickering, or further mod action will follow.

Replying to this modbox in thread will be off topic  Posted By: Cuddles

 

[tusenfem]

They gain energy by ramping across a DL and the plasma gets it kinetic energy from the particles impinging on the anode and cathode side of the DL.

michaelsuede, you still don't get it, the double layer in the experiments is accelerating the particles in the wrong direction. In Fig. 2 of the Gekelman paper, the DL's electric field is pointed in the direction into (or out of) the paper, which would be the axial or Y-direction. Reconnection is accelerating the particles in the X-direction, perpendicular to the axis of the plasma chamber.

Given that differing plasmas will create a double layer, this seems like the only logical conclusion as to the explaination of magnetic reconnection.

There is no such double layer, because there is no real boundary, there is a gradual change of the magnetic field from one side to the other, there may be a gradual change of the density from one side of the other. If anything, say that these would be two differing plasmas, then the double layer would be pointed in the Z-direction (again the wrong direction) and it would NOT accelerate particles the way you think they will, like in a current carrying plasma. Please go study the difference between a current carrying double layer and a non current carrying double layer.

Let us not forget that MHD theory is incapable of describing the mechanics of a DL and therefore neglects the DL as the cause of magnetic reconnection.

Yeah yeah, whatever, so MHD is a bunch of crap then?

MDH, the way Alfvén developed it, can also not describe reconnection, because for reconnection there has to be a resistivity in the plasma, and that is why e.g. numerical codes use resistive (Hall) MHD to do their modeling.

When your models are predicated on junk science, it is unsurprising that the theories concluded from those models will also be junk science.

It is you who calls MHD junk science, I bet your EU friends will be very happy about that, saying that Alfvén developed junk science.

You have absolutely no knowledge whatsoever about plasma physics and double layers. You have not even shown that your basic knowledge of electrodynamics is correct (magnetic field of a charged sphere comes in mind). So, why don't you go study the Yamada et al. (2010) paper.

 

[michaelsuede]

I'm not sure which of the several Stenzel and Gekelman papers I linked that you are referring to, but I don't see "wrong way" current flow in any of them that is unexplained in the papers as being atypical of reconnection observations.

Papers on double layer formation:

Lessons from laboratory experiments on reconnection
http://plasma.physics.ucla.edu/web pdf's/46. Lessons from Lab..pdf

Double layer formation during current sheet disruptions in a reconnection experiment
http://plasma.physics.ucla.edu/Older Publ. PDF/28. 1982_ Double Layer.pdf

Magnetic Field Line Reconnection Experiments, 5. Current Disruptions and Double Layers
http://plasma.physics.ucla.edu/Older Publ. PDF/29. JGR1983-Current Disrupt.pdf

Laboratory experiments on current sheet disruptions, double layers turbulence and reconnection
http://adsabs.harvard.edu/full/1985IAUS..107...47S

Magnetic-field aligned electric fields in collisionless space plasmas – a brief review
http://www.geofisica.unam.mx/divulgacion/geofinternacional/iframes/anteriores/2004/02/Falthamar.pdf


And yes, MHD is a bunch of crap when it comes to modeling dynamic interacting plasma systems.

Let us quote Alfven on MHD theory:

In Cosmical Electrodynamics, I tried to give a survey of a field in which I had been active for about two decades. In one of the chapters, I treated magnetohydrodynamic waves. I pointed out that in an infinitely conductive magnetized fluid the magnetic field lines could be considered as "frozen" into the medium -- under certain conditions -- and this concept made it possible to treat the waves as oscillations of the frozen-in medium.

The "frozen-in" picture of magnetic field lines differs from Maxwell's views. He defined a magnetic field line as a line which everywhere is parallel to the magnetic field. If the current system which produced the field changes, the magnetic field changes and field lines can merge or reconnect. However, if the current system is constant the magnetic field is also constant. To speak of magnetic field lines moving perpendicular to the field makes no sense. They are not material.

In a detailed analysis of the motion of magnetic lines of force, Newcomb (1958) has demonstrated that "it is permissible to ascribe a velocity v to the hne of force if and only if Vx(E x v x H) vanishes identically."

I thought that the frozen-in concept was very good from a pedagogical point of view, and indeed it became very popular. In reality, however, it was not a good pedagogical concept but a dangerous "pseudo-pedagogical concept." By pseudo-pedagogical I mean a concept which makes you believe that you understand a phenomenon whereas in reality you have drastically misunderstood it.

I never totally believed in it myself. This is evident from the chapter on "Magnetic Storms and Aurora" in the same monograph. I followed the Birkeland-St6rmer general approach; but, in order to make that applicable to the motion of low-energy particles in what is now called the magnetosphere, it was necessary to introduce an approximate treatment (the "guiding-center" method) of the motion of charged particles. (As I have pointed out in CP, III. 1, I still believe that this is a very good method for obtaining an approximate survey of many situations and that it is a pity that it is not more generally used.) The conductivity of a plasma in the magnetosphere was not relevant.

Some years later criticism by Cowling made me realize that there was a serious difficulty here. According to Spitzer's formula for conductivity, the conductivity in the magnetosphere was very high. Hence the frozen-in concept should be applicable and the magnetic field lines connecting the auroral zone with the equatorial zone should be frozen-in. At that time (-- 1950) we already knew enough to understand that a frozen-in treatment of the magnetosphere was absurd, but I did not understand why the frozen-in concept was not applicable. It gave me a headache for some years.

In 1963 Carl-Gunne F_ilthammar and I published the second edition of Cosmical Electrodynamics (Alfv6n and F_ilthammar, 1963). He gave a much higher standard to the book and new results were introduced. One of them was that a non-isotropic plasma in a magnetic mirror field could produce a parallel electric field Ell. We analyzed the consequences of this in some detail and demonstrated with a number of examples that in the presence of an Ell, the frozen-in model broke down. On page 191 we wrote:

"In low density plasmas the concept of frozen-in lines of force is questionable. The concept of frozen-in lines of force may be useful in solar physics where we have to do with high- and medium-density plasma, but may be grossly misleading if applied to the magnetosphere of the earth. To plasma in interstellar space it should be applied with some care."

Stenzel and Gekelman repeatedly point out that MHD is incapable of accounting for the mechanics of the double layer and that MHD theory breaks down at the inner region of current sheets.

 

[Ziggurat]

Let us quote Alfven on MHD theory:

Yes, let's do so. But now let's try to actually understand what he's saying:

In one of the chapters, I treated magnetohydrodynamic waves. I pointed out that in an infinitely conductive magnetized fluid the magnetic field lines could be considered as "frozen" into the medium -- under certain conditions -- and this concept made it possible to treat the waves as oscillations of the frozen-in medium.

So right off the bat, we're not even dealing with magnetohydrodynamics, we're dealing with an approximation of magnetohydrodynamics.

The "frozen-in" picture of magnetic field lines differs from Maxwell's views. He defined a magnetic field line as a line which everywhere is parallel to the magnetic field. If the current system which produced the field changes, the magnetic field changes and field lines can merge or reconnect.

So we have an admission by Alfven that according to Maxwell, magnetic fields can "reconnect". He contrasts this with the "frozen-in" picture which he says does not match the Maxwell picture.

I thought that the frozen-in concept was very good from a pedagogical point of view, and indeed it became very popular. In reality, however, it was not a good pedagogical concept but a dangerous "pseudo-pedagogical concept." By pseudo-pedagogical I mean a concept which makes you believe that you understand a phenomenon whereas in reality you have drastically misunderstood it.

So what's he labeling as a pseudo-pedagogical concept"? Not magnetic reconnection, not MHD, but the frozen-in concept. Which, again, is an approximation of MHD, and which DOES NOT match the Maxwell picture which allows for magnetic reconnection.

So nowhere in your quote does Alfven object to MHD or magnetic reconnection. Moreover, even his objections to the frozen-in concept are clearly not categorical:

The concept of frozen-in lines of force may be useful in solar physics where we have to do with high- and medium-density plasma

So all he's saying here is that the concept of frozen-in fields (which is different than magnetic reconnection) is not always applicable, and should be used with care. As an approximation of MHD, it may be a good approximation in some cases but not in others. So MHD itself, without this approximation, should therefore be more broadly applicable.

Alfven isn't saying what you seem to think he is saying. This is no surprise.

 

[tusenfem]

I'm not sure which of the several Stenzel and Gekelman papers I linked that you are referring to, but I don't see "wrong way" current flow in any of them that is unexplained in the papers as being atypical of reconnection observations.

And yes, MHD is a bunch of crap when it comes to modeling dynamic plasma systems.

Let us quote Alfven on MHD theory:

Then maybe you should look up post 105 where I comment on the last paper that you quote in post 102. Read my post 105 again and read my explanation about DLs above again, then think once more about what you write (quoted above).

Just to be clear:
In Fig. 2 of said paper you see the X-Z plane of the experiment which is perpendicular to the axis of the plasma device. It shows the magnetic field topology and the plasma flow, both typical for reconnection.
The current sheet is in the middle at Z=0, going into (or out of) the plane of the figure. The current is flowing in the Y direction.
Gekelman increases the voltage over the machine, driving stronger current in the Y direction, thus creating double layers which will accelerate particles in the Y direction (that is perpendicular to the direction in which reconnection accelerates particles, which is in the X direction in the experiment). Therefore, these double layers, artificially created after reconnection is already taking place, cannot and will not accelerate the particles in the reconnection exhausts.

It is really very simple, you just have to keep the coordinate system in mind, and then it is self explanatory.

MHD is a wonderful tool, for those who know how to use it, which would be any plasma(astro)physicist these days. The comments by Alfvén stem from a time when MHD was used as a tool without thinking about the how and what. Frozen in condition was assumed to be true, and that was that.
Nowadays we get taught that that cannot be. No plasma is infinitely conducting, and thus there is a so called diffusion time of the plasma. The better the conductivity, the longer the time. Then for processes that are shorter than the diffusion time, the frozen in condition can be assumed valid, for processes that take longer the frozen in condition cannot be used.

MDH is an averaged plasma physcis theory, over the longest time and length scales of the plasma. So, whenever you are modeling stuff that is on scales much larger than the greatest gyroradius and on time scales longer than the longest gyroperiod, MDH is valid. If you want to look at smaller scale processes, then you have to revert to plasma physics.

Again, it is all very simple.

In the Earth's magnetosphere, for example, many a process can be described with MHD and even with the frozen in condition, but other processes not. Here my good friend Tony Lui discusses regions in the Earth's magnetotail where the frozen in condition breaks down.

 

[michaelsuede]

So nowhere in your quote does Alfven object to MHD or magnetic reconnection.

Ok

From the next page:

Since then I have stressed in a large number of papers the danger of using the frozen-in concept. For example, in a paper "Electric Current Structure of the Magnetosphere" (Alfv6n, 1975), I made a table showing the difference between the real plasma and "a fictitious medium" called "the pseudo-plasma," the latter having frozen-in magnetic field lines moving with the plasma. The most important criticism of the "merging" mechanism of energy transfer is due to Heikkila (1973) who with increasing strength has demonstrated that it is wrong. In spite of all this, we have witnessed at the same time an enormously voluminous formalism building up based on this obviously erroneous concept. Indeed, we have been burdened with a gigantic pseudo-science which penetrates large parts of cosmic plasma physics. The monograph CP treats the field-line reconnection (merging) concept in I. 3, II. 3, and I1.5. We may conclude that anyone who uses the merging concepts states by implication that no double layers exist.

A new epoch in magnetospheric physics was inaugurated by L. Lyons and D. Williams' monograph (1985). They treat magnetospheric phenomena systematically by the particle approach and demonstrate that the fluid dynamic approach gives erroneous results. The error of the latter approach is of a basic character. Of course there can be no magnetic merging energy transfer.

I was naive enough to believe that such a pseudo-science would die by itself in the scientific community, and I concentrated my work on more pleasant problems. To my great surprise the opposite has occurred; the "merging" pseudo-science seems to be increasingly powerful. Magnetospheric physics and solar wind physics today are no doubt in a chaotic state, and a major reason for this is that some of the published papers are science and part pseudoscience, perhaps even with a majority for the latter group.

In those parts of solar physics which do not deal with the interior of the Sun and the dense photospheric region (fields where the frozen-in concept may be valid), the state is even worse. It is difficult to find theoretical papers on the low density regions which are correct. The present state of plasma astrophysics seems to be almost completely isolated from the new concepts of plasma which the in situ measurements on space plasma have made necessary (see Section VIII).

I sincerely hope that the increased interest in the study of double layers -- which is fatal to this pseudoscience -- will change the situation. Whenever we find a double layer (or any other Ell _ 0) we hammer a nail into the coffin of the "merging" pseudo-science.

 

[tusenfem]

I sincerely hope that the increased interest in the study of double layers -- which is fatal to this pseudoscience -- will change the situation. Whenever we find a double layer (or any other Ell _ 0) we hammer a nail into the coffin of the "merging" pseudo-science.

Like I already said, DLs are ubiquitous in the magnetospheric region above the aurora, a region where nobody ever would expect "merging" to happen.

Sorry, Alfven was a great guy, but there were things that he got wrong.

 

[Ziggurat]

Ok

From the next page:

Nope, he's still just objecting to the misuse of the frozen-in concept.

 

[michaelsuede]

Like I already said, DLs are ubiquitous in the magnetospheric region above the aurora, a region where nobody ever would expect "merging" to happen.

Sorry, Alfven was a great guy, but there were things that he got wrong.

Alfven didn't get anything wrong.

He explicitly predicted the existence of those double layers before they were confirmed by satellites.

He is referring to finding double layers in reconnection events.

 

[Tubbythin]

Alfven didn't get anything wrong.

And what makes you so unequivocally sure of this?

ETA: You've even explicitly posted his own word saying that he got something wrong. So either he did get that wrong or he was wrong when he said he was wrong. Either way he was clearly wrong at some point.

 

[michaelsuede]

Just to be clear:
In Fig. 2 of said paper you see the X-Z plane of the experiment which is perpendicular to the axis of the plasma device. It shows the magnetic field topology and the plasma flow, both typical for reconnection.
The current sheet is in the middle at Z=0, going into (or out of) the plane of the figure. The current is flowing in the Y direction.
Gekelman increases the voltage over the machine, driving stronger current in the Y direction, thus creating double layers which will accelerate particles in the Y direction (that is perpendicular to the direction in which reconnection accelerates particles, which is in the X direction in the experiment). Therefore, these double layers, artificially created after reconnection is already taking place, cannot and will not accelerate the particles in the reconnection exhausts.

http://plasma.physics.ucla.edu/web pdf's/46. Lessons from Lab..pdf

You can't deal with the center of current sheets using MHD theory and expect to get anywhere.

 

[michaelsuede]

And what makes you so unequivocally sure of this?

ETA: You've even explicitly posted his own word saying that he got something wrong. So either he did get that wrong or he was wrong when he said he was wrong. Either way he was clearly wrong at some point.

He said he was wrong about MHD theory being something valid and useful.

He then went on to explain why MHD theory is a load of junk science.

So yes, he did get something wrong.

And the thing he got wrong is what modern cosmology is predicated on.

 

[Ziggurat]

Alfven didn't get anything wrong.

As Tubbythin asked, how do you know? Seriously, on what basis can you make this rather extraordinary claim? I don't know of any scientist of any note that I would say that about. So that would make him unique, if true.

But how would you know? In order to determine if he got everything right, you'd need to be able to evaluate everything he said. That would require considerable expertise. And you've presented no evidence that you have any such expertise. You have, in fact, failed to demonstrate even basic competence in regards to electrodynamics. So not only have you not supported your claim with any evidence, we also have no reason to trust your ability to make such an evaluation.

He explicitly predicted the existence of those double layers before they were confirmed by satellites.

Getting something right, even something amazing, doesn't mean you never get anything wrong.

 

[Ziggurat]

So yes, he did get something wrong.

That was a quick retreat. But I doubt you actually understand the full significance of this admission.

And the thing he got wrong is what modern cosmology is predicated on.

Nope. Modern cosmology is pretty much indifferent to those issues. But perhaps you're confused about the difference between cosmology and astrophysics.

 

[tusenfem]

You can't deal with the center of current sheets using MHD theory and expect to get anywhere.

And clearly you have not understood a word of what I have written. I have not mentioned MDH, I have just described what happens in Stenzel & Gekelman's experiment. I have explained about the direction of the double layer.

Care to actually put some effort in reading what I write instead of glancing over and then come back with nonsense plattitudes?

Maybe you should start to explain why the centre of a current sheet cannot be modeled by MHD.

 

[W.D.Clinger]

And yes, MHD is a bunch of crap when it comes to modeling dynamic interacting plasma systems.

Alfven didn't get anything wrong.

He said he was wrong about MHD theory being something valid and useful.

He then went on to explain why MHD theory is a load of junk science.
So yes, he did get something wrong.
And the thing he got wrong is what modern cosmology is predicated on.

For just three consecutive posts, michaelsuede, that's a mighty impressive load of fail.

That was a quick retreat. But I doubt you actually understand the full significance of this admission.

If I understand michaelsuede correctly, he's telling us we should trust michaelsuede's interpretation of Alfvén's keynote address because Alfvén invented "a load of junk science" and/or "crap".

Or maybe michaelsuede is saying we should trust michaelsuede's interpretation of Alfvén's keynote address because Alfvén was wrong when Alfvén claimed to have invented "a load of junk science" and/or "crap".

Or maybe michaelsuede is saying we should trust michaelsuede's interpretation of Alfvén's keynote address because michaelsuede is uniquely qualified to interpret the writings of a man who was so brilliant that he conned The Nobel Foundation into giving him a prize for inventing "a load of junk science" and/or "crap".

It's hard to tell what michaelsuede thinks he's thinking.

 

[Michael Mozina]

So say you.

No, so said Alfven at least a dozen times in his keynote speech that I provided you with earlier.

As noted below, however, we have no reason to believe you actually understand what Alfvén was condemning.

Ya right. Nice rationalization and all, but his double layer paper and every double layer in plasma events was another 'nail in the coffin' of the theory according to Alfven. You've got particles inside a double layer at the point of "reconnection" so your theory is dead and buried according to the guy the wrote MHD theory.

In recent months, I thought you had backpedalled from your denial of magnetic reconnection's existence and had begun to say you objected to it only because of its name.

Me personally? I personally "backpeddled" several years ago at space.com actually after seeing a paper by Birn.

(Your objection to its name was based on your failure to understand it, but we needn't pursue that tangent.) Do we need to quote your backpedalling from all those other threads?

Nope. I'm still sure it's "circuit reconnection" with a stupid name.

Did you guys decide upon *THE* lab oriented paper on MR theory that eliminated other mundane energy transfers from consideration yet?

 

[tusenfem]

He said he was wrong about MHD theory being something valid and useful.

He then went on to explain why MHD theory is a load of junk science.

So yes, he did get something wrong.

And the thing he got wrong is what modern cosmology is predicated on.

No, MHD is valid and useful.
What Alfvén complained about was people using the frozen in concept on face value, without checking whether it was appropriate to use.
Modern cosmology is not based on MDH.

 

[Michael Mozina]

No, why don't YOU explain how induction, "particle reconnection", circuits, collisions or whatever other pink unicorns you can come up with works to explain all the observations .

Dungey made it quite clear that reconnection is the only viable process.

Alfven made it quite clear you could model it in terms of circuits as did Mann and Onel too. So what? You guys only do the B orientation and act like the E orientation isn't equally viable. It's stupid of course to do that of course since Maxwell's equations allow them to be interchanged, but that is in fact exactly what you do. Go figure.