Problems With Magnetic Reconnection

tusenfem said:
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.
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He would *STILL* complain about it since you're talking about *CURRENT CARRYING* plasma, and in such situations he *ALWAYS* rejected MR theory and ALWAYS preferred a "circuit/particle" orientation to a "magnetic/field" orientation.
 
Michael M, what are your views on Michael S's claim that "MHD theory is a load of junk science"?
 
michaelsuede said:
He explicitly predicted the existence of those double layers before they were confirmed by satellites.
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Methinks, you are mixing up Alfvén with Birkeland.
Not double layers were predicted, but field aligned currents.
Double layers were already studied in some form by Langmuir.
The real study in the lab was started by Schoenhuber in the late 50s.
Alfvén did propose that they might exist above the auroral regions.
 
tusenfem said:
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.
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I understand your argument, and I also understand why it doesn't hold up as refuting the circuit theory cause of reconnection. You are arguing that the DL can't accelerate particles in the direction of observed reconnection. The paper I just linked demonstrates that this is not true.

You can model the center of a current sheet just fine using MHD.

However, you will not be able to actually give reasons for anything that is observed there without using circuit theory to explain the causative agents behind the instabilities.

And you also can't use MHD to describe what results from those instabilities, such as the formation of double layers.
 
michaelsuede said:
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.
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No this is not the source of energy increase in magnetic reconnection. Double layers and magnetic reconnection are two separate phenomena. They generally occur separately.

There are situations in which evidence for both have been observed. e.g. some solar flares (caused by magnetic reconnection) emit beams of electrons that are thought to be accelerated by DL.
 
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Tubbythin said:
Michael M, what are your views on Michael S's claim that "MHD theory is a load of junk science"?
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I think I felt the same way that Alfven felt and that Michael S still feels about it until I read Birn's paper. It became incredibly clear from those debates (at space.com) that it was "circuits" and "particles" doing the actual "reconnection' inside of a "double layer". Whereas Alfven literally "rejected" the whole B orientation under such conditions, I couldn't personally bring myself to do that. The B's however can be converted to E's and the whole thing becomes a PARTICLE/CIRCUIT problem. I too prefer the particle/circuit orientation in current carrying plasma so I call it "circuit reconnection". It's not actually any magnetic lines that do any "reconnecting", it's the circuits and the particles that "reconnect" (literally slam into one another) at the point of intersection inside of a double layer. Any time Alfven found a double layer, he claimed it put another nail in the coffin of MR theory. MR theory will always be 'pseudoscience" because it's only every going to be "pseudo-correct". It's not however the magnetic lines that "reconnect", so it will never be "100% correct" as long as it has such a stupid name.
 
Michael Mozina said:
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.
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No, neither of those do what you say.
Alfvén used a double layer to unwind a magnetic loop on the sun.
Alfvén used an exploding double layer and said it was what happens in a flare, but arguments have been made that it will not come so far, for various reasons (see your own thread).
Onel and Mann describe large e fields and use circuits. That has been discussed and has nothing to do with reconnection.

Please give me the E orientation of magnetic reconnection (or should that be electric reconnection then ???). I asked that before and got a nonsense answer. But one can hope.

michael2 should get something together.
 
Michael Mozina said:
I think I felt the same way that Alfven felt and that Michael S still feels about it until I read Birn's paper. It became incredibly clear from those debates (at space.com) that it was "circuits" and "particles" doing the actual "reconnection' inside of a "double layer". Whereas Alfven literally "rejected" the whole B orientation under such conditions, I couldn't personally bring myself to do that. The B's however can be converted to E's and the whole thing becomes a PARTICLE/CIRCUIT problem. I too prefer the particle/circuit orientation in current carrying plasma so I call it "circuit reconnection". It's not actually any magnetic lines that do any "reconnecting", it's the circuits and the particles that "reconnect" (literally slam into one another) at the point of intersection inside of a double layer. Any time Alfven found a double layer, he claimed it put another nail in the coffin of MR theory. MR theory will always be 'pseudoscience" because it's only every going to be "pseudo-correct". It's not however the magnetic lines that "reconnect", so it will never be "100% correct" as long as it has such a stupid name.
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I asked what you thought about MS's opinions on MHD, not on MR.
 
Reality Check said:
michaelsuede said:
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.
[/quote[
No this is not the source of energy increase in magnetic reconnection. Double layers and magnetic reconnection are two separate phenomena. They generally occur separately.

There are situations in which evidence for both have been observed. e.g. some solar flares (caused by magnetic reconnection) emit beams of electrons that are thought to be accelerated by DL.
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In the lab, they do not occur separately.

From what we know to be true about the laboratory proven physics of "reconnection" - the DL plays a role as a causative agent involved in the transfer of energy.

Neglecting the existence of DLs by modeling reconnection events entirely in MHD frameworks does not mean they do not exist in real life.

MHD theory is incapable of accounting for them, which is why they never pop up in discussions of reconnection.

Given that we know localized instabilities will generate regions of varying voltage / potential, we know that there will be DLs formed.
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Michael Mozina said:
He would *STILL* complain about it since you're talking about *CURRENT CARRYING* plasma, and in such situations he *ALWAYS* rejected MR theory and ALWAYS preferred a "circuit/particle" orientation to a "magnetic/field" orientation.
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That is just idiotic, MM.
Why on earth or in space or on the sun, would a current carrying plasma not be able to have magnetic reconnection? It is a frakking requirement of MHD or Maxwell's equations that if you have two regions with oppositely directed magnetic field that there is a current flowing, which facilitates the changing direction and magnitude of the magnetic field.

So, when are you going to present us your circuit model of reconnection? I made a start for you in the other thread, but when you found that you actually had to do some real work, you suddenly gave up.

Guess you can only write misconceptions about plasma physics, go figure.
 
tusenfem said:
That is just idiotic, MM.
Why on earth or in space or on the sun, would a current carrying plasma not be able to have magnetic reconnection? It is a frakking requirement of MHD or Maxwell's equations that if you have two regions with oppositely directed magnetic field that there is a current flowing, which facilitates the changing direction and magnitude of the magnetic field.

So, when are you going to present us your circuit model of reconnection? I made a start for you in the other thread, but when you found that you actually had to do some real work, you suddenly gave up.

Guess you can only write misconceptions about plasma physics, go figure.
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The math is beyond him. Beyond MM too.
 
tusenfem said:
No, neither of those do what you say.
Alfvén used a double layer to unwind a magnetic loop on the sun.
Alfvén used an exploding double layer and said it was what happens in a flare, but arguments have been made that it will not come so far, for various reasons (see your own thread).
Onel and Mann describe large e fields and use circuits. That has been discussed and has nothing to do with reconnection.

Please give me the E orientation of magnetic reconnection (or should that be electric reconnection then ???). I asked that before and got a nonsense answer. But one can hope.

michael2 should get something together.
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The plasma expands primarily in the direction of ion flow:
http://plasma.physics.ucla.edu/web pdf's/46. Lessons from Lab..pdf

Toward the cathode.
 
michaelsuede said:
In the lab, they do not occur separately.
...snipped unsupported assertions...
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In the lab they do occur separately. There are many magnetic reconnection experiments.
In some experiments DLs are also detected, e.g. these 1982 and 1983 experiments

Double layer formation during current sheet disruptions in a reconnection experiment
N.B. AFAIK current sheet disruption happens after the magnetic reconnection event.

Magnetic Field Line Reconnection Experiments, 5. Current Disruptions and Double Layers
 
tusenfem said:
What kind of comment is that supposed to be?
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It is certainly a strange reply. The paper turns out to be
Lessons from Labatory Experiments on Reconnection, R.L. Stenzel, W. Gekelman and J. M. Urrutia 1986

So he cites people who say that magnetic reconnection exists and worked with it a lot in the 1980s :jaw-dropp!

ETA: There is that double layers can be caused by current disruption.
ETA2: And the paper that he cites proves that the current disruption and so the DL happens after the magnetic reconnection!
 
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Reality Check said:
In the lab they do occur separately. There are many magnetic reconnection experiments.
In some experiments DLs are also detected, e.g. these 1982 and 1983 experiments

Double layer formation during current sheet disruptions in a reconnection experiment
N.B. AFAIK current sheet disruption happens after the magnetic reconnection event.

Magnetic Field Line Reconnection Experiments, 5. Current Disruptions and Double Layers
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The DLs are the mechanism that imparts kinetic energy to the particles.

As I stated earlier, what causes the instabilities in the current sheet is external to the sheet and a property of the circuit. You can have all sorts of instabilities without them resulting in the formation of a double layer.

However, it is the formation of a double layer that drives 'reconnection'. An explosive release of energy can not occur without the onset of a DL.
 
michaelsuede said:
I'll agree to magnetic reconnection if you agree to that paper's theory about what causes it.
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That 1986 (see below about why I have this in bold) paper says nothing about what causes magnetic reconnection.
It states that magnetic reconnection exists and presumably the authors are capable of reading basic textbooks on electromagnetism and seeing that the cause is the reconfiguration of magnetic fields as allowed by Maxwell's laws.

It says that after the magnetic reconnection there is current sheet disruption. That current sheet disruption can cause DLs.

So I guess that you "agree to magnetic reconnection" :D.

The point of the paper is that there is a regime in which the usual MHD concepts (e.g. Alfven waves and frozen-in magnetic fields) are violated and have to be replaced with other concepts such as Whistler waves.

That is basically what Alfven said, i.e. the frozen-in magnetic field approximation was being applied to inappropriate regimes.
That is why modern (2011) plasma physicists are careful to not apply the frozen-in magnetic field approximation inappropriately. In these regimes they use resistive MHD rather than ideal MHD. When the plasma is collisionless, they add in the Hall effect.
 
michaelsuede said:
The DLs are the mechanism that imparts kinetic energy to the particles.
...
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Repeating a wrong assertion does not make it true.
When there is just magnetic reconnection, magnetic reconnection is the mechanism that imparts kinetic energy to the particles.
When there is magnetic reconnnetion + DLs then both mechanisms impart kinetic energy to the particles.
The formation of the DLs happens after the magnetic reconnection.
See Figure 9 in Lessons from Labatory Experiments on Reconnection, R.L. Stenzel, W. Gekelman and J. M. Urrutia 1986 :jaw-dropp!

Can you read it, michaelsuede?
Can you see the disruption happening after the reconnection, michaelsuede?
Can you understand the abstract where it stated that the double layers happen after the disruption, michaelsuede?
 
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