Magnetic reconnection and physical processes

[Zeuzzz]

Actually, its probably best I put this post here.

Really, reconnection cannot happen? Do you have any proof for that?
And please give us the description of current disruption re-organization of the magnetic field topology.
Don't forget that in the Earth's magnetotail we have a enormous amount of observations of magnetic field and plasma that all totally agree with the model of magnetic reconnection. I would love to see your explanation.

While the explanation is not strictly current disruption, it follows a similar approach, instead of using magetic field lines and flux transfer it considers the way that the currents and resulting dynamo's they produce can be a viable contendor to magnetic reconnection.

Instead of relying on the concept of magnetic reconnection, world authority on magnetosphric physics Syun-Ichi Akasofu and others, have recently shown in a publication in the IEEE transactions on plasma science, that it may be worthwhile to consider that the solar wind–magnetosphere dynamo generates two solenoidal currents in the magnetotail. The flux transfer can be understood in terms of an increase of the solenoidal currents caused by an increase of ε. Changes of the magnetic field configuration that are associated with the so-called “southward turning” of the IMF vector can be explained by an increase of the dynamo power ε.

Long Standing Unsolved Problems in Solar–Terrestrial Physics - Plasma Science, IEEE Transactions on, Dec. 2007

As ε increases, the two solenoidal currents increase in the magnetotail, and the resulting increase of the antiparallel flux can cause changes of the magnetic field configuration in both the dayside and the nightside. The changes are basically the same with those caused by the magnetic flux transfer to the nightside. An enhanced antiparallel field in the magnetotail stretches the dipolar field in the nightside. (Fig. 8).

As will be discussed in the next section, some substorms are triggered by a sudden “northward turning” of the IMF vector after the magnetosphere is primed [26]. As the ε is decreased, the intensity of themagnetotail field is decreased. It has been interpreted, however, that the decrease of the magnetotail field is a proof of magnetic reconnection [13]. This argument forgets the fact that the northward turning indicates a decrease of the solenoidal (cross-tail) current after an enhancement during the period of being primed. Our way of interpreting such phenomena can help in avoiding misinterpretation that the field decrease is caused by magnetic reconnection. This way of consideration, although not quantitative, does not require the knowledge of the reconnection rate, which is uncertain (making the quantitativeness of the MHD simulation somewhat doubtful). It is unfortunate that theorists are not interested in such a simple way of understanding magnetospheric phenomena. This will become more evident in the next section. Thus, this qualitative way may be more accurate than a quantitative misinterpretation based on magnetic reconnection.

[13] M. N. Caan, R. L.McPherron, and C. T. Russell, “Substorm and interplanetary magnetic field effects on the geomagnetic tail lobes,” J. Geophys. Res., vol. 80, pp. 191–194, Jan. 1975.

[26] L. R. Lyons, G. T. Blanchard, J. C. Samson, R. P. Lepping, T. Yamamoto, and T. Moretto, “Coordinated observations demonstrating external substorm triggering,” J. Geophys. Res., vol. 102, no. A12, pp. 27 039–27 051, Dec. 1, 1997.

Much more plausable than MR in my opinion, as by focussing on electric field and current as primary quantities you can consider an analysis based on detailed particle dynamics, instead of the interaction of ambiguos field lines and MHD terms, that lead to many problems. He ellaborates on this model further later, but i'm restricted to small quote size on this forum, and people throw a fit when I post stuff not in quotes. I suspect that such electrical solutions like this are evident in most situations where MR is utilised, and can usually provide a much more detailed explanation of what is physically occuring than MR does. I am not saying that MR is completely redundant, it can be useful in working out flux transfer, but the question is whether MR is the final tool in understanding substorms. Although many MHD simulations have been successful in reproducing substorm-like features, they have not actually come up with a chain of processes that lead to a substorm onset, partly because the reconnection rate is arbitrarily set.

 

[sol invictus]

Yeah, go on then. Hows about addressing the other part of this sentence that you cut out above where I actually explain the reasoning for this statement?

The reasoning was obviously false, so I didn't bother. If you had bothered to read what I said, you would have noticed that I said the B field lines contain all the information "in the limit large line density". The lines are not really discrete in that limit.

Look - if you drew the field using little arrows attached to each point, you could have made the same objection. But representing fields by assigning a magnitude and direction to each point is the standard way to do it, so your objection is obviously wrong.

As for the proof, it's trivial. You agree any vector field is specified by a magnitude and direction at each point. Fine - define the magnitude to be the line density around a point (number of lines within a volume of size epsilon) divided by the average line density, and the direction to be the tangent to the line nearest to the center of the epsilon-volume. Then take the limit I referred to (line density to infinity) while taking epsilon to zero. That gives you a continuous function that assigns a magnitude and direction to every point. All that remains is to prove it's the same function as the field we started with.

But that's true by definition. The direction must be the same, because the lines are always in the direction of the field. The density gives the field strength if we choose it to - in fact that's completely up to you when you draw the lines.

Not at all. The fact that you say this merely shows that you either dont comprehend what I am saying or just deny that it is a viable position to take. Magnetic field “lines” are simply graphic artifices to aid visualization of the field’s strength and direction, the magnetic field they are representing is however a continuum, not a set of discrete lines. So basing things like MR on the lines themselves, that we put in, is plain wrong.

I have just proven that magnetic field lines are a fully valid representation of the magnetic field. Anything a field can do the lines can do, and visa versa.

Can you not see how the actual field lines themselves have become Reified in this sense? This is a classic logical fallacy, see: Reification (fallacy)

Zeuzzz, please answer this question: in what sense is the magnetic field, specified however you prefer, more "real" than the field lines?

The answer is that it's precisely no more or less real. Both those things are mathematical models for describing the world. In this case they happen to be exactly the same, but more generally, whenever we speak about physics beyond data we are "reifying" some mathematical concept. Which is just fine, and is obviously not a "fallacy".

Your just being pedantic here. Lets change that to the energy stored around any point then, and you certainly cant say that.

Of course I can! That field is only zero at one single point. Do you really not understand this?

I fail to see how lines representing nothing more than equal values of vectors in a vector field can become tangled. Something being tangled implies physical processes. They are not tangled, they can not fling anything out, they are just doing what they always do, representing the continuum of the infinite vector field.

Have you forgotten yet again what the density of lines means?

And I suggest you buy the slightly more up to date Eos, Transactions, American Geophysical Union, Vol. 88, 2007, where respected astronomer Carl-Gunne Fälthammar says the exact same thing about the idea of moving magnetic field lines that I just stated in the above quote.

For learning EM, rather than Griffiths' Introduction to Electrodynamics you recommend an article by some crackpot in an American Geophysical Union paper?

 

[tusenfem]

So basically what he is saying is that the ε parameter, describing sort of the solar wind motional electric field increases the cross tail current (in the solenoids) and then when the IMF changes the ε decreases and the field in the lobe decreases. This is fine with me, no problem what soever.

But, this only looks at the stretching of the magnetic field in the tail, and the cross tail current increasing and decreasing. What you present here is a global view of the m-tail. but this nicely goes by all the observations that have been made, e.g. with Cluster, of the physics inside the current sheet, where we see the topology of the field change from "bent towards the Earth" to "bent away from the Earth", the plasma in and out flows, the currents (cross tail, Hall and field aligned), which all point to reconnection. Even my good friend Tony Lui will not disagree on that, even though he is an "inward-out" current disruption proponent.

You can object what you want against the MHD codes that simulate reconnection, but it is rather hard to take observations which fit the theoretical model like a $10000 suit.

Methinks you have copied the wrong part of the paper here.

And the fact that you still do not understand that Maxwell allows us to look at Bv OR at Ej, whichever one is easier for the problem is problematic. Yes, I could sit down for a full weekend and write down Petchek reconnection in the Ej viewpoint, but it would be a lot of writing and come up with very very complicated models, whereas when I do it in the Bv (the equally valid format) it is so much more simple.

 

[tsig]

I've been engaged to the same woman five times. Numerous physical processes were involved. Each time an immeasurably large amount of energy was released. Oh, and I'm about to move to the city where she lives.

I've been married to the same woman for 40 years. Many large energys have been release and we look forward to more.

 

[tusenfem]

Yes, thanks. Planetary magnetism is the (an) other end of the planetary science spectrum from my field (isotope cosmochemistry), but I've been on enough panels dealing with magnetic reconnection to want to understand it better. (Most funding panels combine experts from various fields who don't necessarily all understand one another's area.)

Are you working on Venus Express?

interesting! cosmochemistry! guess you can come up with mind altering drugs that are really spacing you out! (owwww that is sooooo bad)

Yes, I work on Venus Express and have strong indications that reconnection also takes place there.

 

[Zeuzzz]

For learning EM, rather than Griffiths' Introduction to Electrodynamics you recommend an article by some crackpot in an American Geophysical Union paper?

So we can now add Carl-Gunne Fälthammar to the, now incredibly long, list of people Sol thinks are crackpots. I presume that also since his work was published in a reputable peer reviewed journal we can add the people that approved his publication to the list aswell?

This list is getting on nicely now, three nobel laureates and (at least) thirty peer reviewed scientists, including various directors of institutes and founders of scientific institutions. To clarify, you still think that Asofu is a crackpot aswell?

Who are you?



Dare is ask why Fälthammars peer reviewed publication on the concept of moving magnetic field lines has invoked such a reaction? I find his point that belchers moving magnetic field line velocity is only valid when B × curl [B(E•B/B²)] = 0 quite satisfactory, likewise his example of a time-independent magnetic dipole field in the presence of a homogeneous electric field parallel to the dipole axis. But I am presuming you have a good reason to dismiss this?

 

[tusenfem]

Interestingly, reading through Karl-Gunne's (not really a crackpot, Sol, but he is aging and seems to follow his predecessor Alfvén. I really liked him when I was at his lab in Stockholm) paper once more I see that he writes (regarding the non-validity of equation 2):

In fact, the most interesting plasma physics occurs precisely where and because this equation is not satisfied, such as the auroral acceleration region, magnetic field reconnection, turbulence, shocks, and many wave modes.

Ouch! Zeuzzz

 

[Zeuzzz]

Ouch! Zeuzzz

Not really, I never claimed it was disproving magnetic reconnection, I used it back up my statement about the motion of field lines being inherently meaningless in general. His personal views on MR are a separate issue.

 

[sol invictus]

Well, in fairness I don't know much about him. From the quote it sounds like he has indeed followed in the footsteps of Alfven, who did great work early in his career before falling into crank-dom. (Incidentally this is a common pattern: I could list many Nobel laureates that have followed that path, several of whom I know personally.) But without reading the paper it's hard to know for sure.

Anyway, Zeuzzz' suggestion that one should learn basic E&M from that article rather than from a text like Griffiths is totally absurd.

 

[sol invictus]

Not really, I never claimed it was disproving magnetic reconnection, I used it back up my statement about the motion of field lines being inherently meaningless in general. His personal views on MR are a separate issue.

The farce continues....

So he is a "respected astronomer" whose work one should consult to learn basic E&M, and his statements on moving field lines are of course totally valid... but his statement in the same article about magnetic RC are "personal views" and to be ignored?

 

[tusenfem]

The farce continues....

So he is a "respected astronomer" whose work one should consult to learn basic E&M, and his statements on moving field lines are of course totally valid... but his statement in the same article about magnetic RC are "personal views" and to be ignored?

Yeah, this is getting more and more complicated, don't know what to believe anymore now.

 

[DeiRenDopa]

The farce continues....

So he is a "respected astronomer" whose work one should consult to learn basic E&M, and his statements on moving field lines are of course totally valid... but his statement in the same article about magnetic RC are "personal views" and to be ignored?

And that's only half of it!

Z has been pretty consistent in stating that there is only One True God and Alfvén its Prophet; but almost equally consistently Z has been saying Fälthammar is a True Disciple of The Prophet (along with Peratt and Lerner).

Now according to Z, The Prophet Declared "Thou Shalt Not Worship False Magnetic Reconnection!", and a Lesser Disciple (Scott) Spake on this Declaration too.

Apparently the resolution of a potential conflict (a True Disciple contradicts The Prophet, as well as a Lesser Disciple) is to allow the possibility that the True Disciple may have been having a bad day (or Bad Day).

 

[Michael Mozina]

This thread is an attempt to try to resolve the long debate on magnetic reconnection that has been ongoing in various threads, which I now feel needs its very own thread. I have spent ages trying to get a concrete definition of magnetic reconnection from someone, everyone seems to give different answers, and there are a lot of separate things that need to be taken into account, so here’s the chance for Sol and others to write exactly what magnetic reconnection is. I am after the whole process, from the topological change in the field lines representing the magnetic vector field around the formation of the neutral point (often respresentaed as an X type neutral line) all the way through to how the energy is physically released from the topology of the lines in this system.

Ah, I see you beat me to this discussion here. I had a similar one on space.com. Burn's presentation of this ideas was the "best" one I found because it explicitly mentioned the "current flow" inside the "magnetic line". Most of them were pure BS, but that one had the physics right as well. I'll see if I can find you a link to the paper tomorrow, or I'll upload it to my website. The paper is on my other computer at the moment.

What became painfully clear to me during these discussions is that the mainstream has the math essentially right, the term itself is a self conflicted bit of nonsense. It was ultimately 'particle reconnection" or "circuit reconnection", but as you of course know, it can't be "magnetic reconnection" because they lack physical substance and form as a whole continuum.

What was also made clear in these discussions is their *complete ignorance* of physics. The act like magnetic lines have a substance and kinetic movement of their own. When you ask them how a magnetic line "stores" "magnetic energy" it never occurs to them it's the kinetic energy of the particles moving inside that magnetic line.

Their math is fine. Their labeling scheme is irrational.

 

[sol invictus]

What was also made clear in these discussions is their *complete ignorance* of physics. The act like magnetic lines have a substance and kinetic movement of their own. When you ask them how a magnetic line "stores" "magnetic energy" it never occurs to them it's the kinetic energy of the particles moving inside that magnetic line.

Oh, really? So... which particles are those for a magnetic field in vacuum? Or did you not know that has an energy density?

What was that about "complete ignorance"?

 

[Michael Mozina]

Oh, really? So... which particles are those for a magnetic field in vacuum? Or did you not know that has an energy density?

What was that about "complete ignorance"?

The problem of course is that in the solar atmosphere, that statement is utterly inapplicable. There is nowhere in interstellar space that is a "pure vacuum", and nowhere in interplanetary or interstellar space where current flow is not occurring. Like I said, you are ignorant of the *REAL PHYSICS* of what is actually occurring in the *real world*. You guys do a little math dance and ignore the physics entirely. In the real world, the only thing capable of "reconnecting" are *particles* and *circuits*. Magnetic lines lack empirical substance, so how in the world do you figure they "disconnect" or "reconnect"?

 

[Ziggurat]

Magnetic lines lack empirical substance, so how in the world do you figure they "disconnect" or "reconnect"?

This is a semantic complaint. Consider the field
[latex]$\vec{B}=by\hat{i} + ax\hat{j}$[/latex]

If we vary a and b, we change the magnetic field. For ALL a < b, the points (-1,1) and (1,1) are connected by a magnetic field line. For ALL a > b, the points (-1,1) and (-1,-1) are connected by a magnetic field line. Whether or not you consider that line real is irrelevant: the field is real, and the rules for drawing the line are unambiguous. So we can call this as magnetic reconnection. You may object to the label, but your objection is purely semantic: what's happening (the change in the magnetic field) is real, and the rules for determining whether or not what's happening fits our definition of the term are clear and consistent.

 

[ben m]

What was also made clear in these discussions is their *complete ignorance* of physics. The act like magnetic lines have a substance and kinetic movement of their own. When you ask them how a magnetic line "stores" "magnetic energy" it never occurs to them it's the kinetic energy of the particles moving inside that magnetic line.

Wow, you just failed freshman physics. Magnetic fields have an energy density which has nothing to do with the energy of the particle (or whatever) responsible for the current. That's how inductors work; every freshman physicist or engineer knows that. Young and Freedman, chapter 30. Griffiths, chapter 7. When you unplug an inductive load (like an iron, or a transformer) from the wall and it makes a spark, that spark is discharging the stored magnetic energy.

I suspect you're going to argue out of habit, but seriously---LOOK IT UP. This is not a mistake, this is not dogma. This is Michael Faraday and th gang doing experiments in the late 1800s. This is the grey box in the back of your computer with the thick colored wires in it. This is also one of the things at work in astrophysical plasmas.

 

[Michael Mozina]

This is a semantic complaint.

No, it's a PHYSICS complaint. You are ignoring or not recognizing the actual physical energy exchange process. At it's most basic level, it is a kinetic energy transfer process between moving charged particles. It is a "circuit reconnection" event where the whole circuit energy of both circuits determines the rate of reconnection. What it cannot *possibly* be is a "magnetic reconnection" event because magnetic fields lack physical substance and they form as a full and complete continuum, without beginning and without end. They are physically incapable of "reconnecting" any any way.

Consider the field
[latex]$\vec{B}=by\hat{i} + ax\hat{j}$[/latex]
[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_1192499b6711ad5d6.gif[/qimg]
If we vary a and b, we change the magnetic field. For ALL a < b, the points (-1,1) and (1,1) are connected by a magnetic field line. For ALL a > b, the points (-1,1) and (-1,-1) are connected by a magnetic field line. Whether or not you consider that line real is irrelevant: the field is real, and the rules for drawing the line are unambiguous. So we can call this as magnetic reconnection. You may object to the label, but your objection is purely semantic: what's happening (the change in the magnetic field) is real, and the rules for determining whether or not what's happening fits our definition of the term are clear and consistent.

Would you agree that we could also rightly call this process "circuit reconnection" or "particle reconnection"? If so, you and I can move beyond semantics as long as you recognize that it is physically impossible for magnetic lines to "reconnect". It therefore makes no sense to call this process "magnetic reconnection". No such thing is actually physically occurring in the plasma. The *particles* reconnect. The *circuits* reconnect, but magnetic lines are physically incapable of disconnecting or reconnecting to any other magnetic line.

 

[Michael Mozina]

Wow, you just failed freshman physics. Magnetic fields have an energy density which has nothing to do with the energy of the particle (or whatever) responsible for the current.

That might have some merit it weren't for the fact that no part of interplanetary space is "current free" and the atmosphere of the sun was a pure vacuum and the sun is solid. In such a case your argument might have merit. In the conditions where these ideas are being suggested, such notions are irrelevant. It's not the magnetic field that does anything, it's the constant "current flow" between the surface of the sun and the heliosphere that does the work. The magnetic fields simply "pinch" the plasma together like in an ordinary plasma ball filament.

That's how inductors work; every freshman physicist or engineer knows that.

Sure. What I'm asking you however is how you intend to apply that in the solar atmosphere.

Young and Freedman, chapter 30. Griffiths, chapter 7. When you unplug an inductive load (like an iron, or a transformer) from the wall and it makes a spark, that spark is discharging the stored magnetic energy.

In that case the "stored magnetic energy" you're talking about is kinetic energy in the one coil that is transferred to the secondary coil. It's still a "kinetic energy" transfer event. The same is true in all 'magnetic reconnection" events in the solar atmosphere. These are also know as "electrical discharge" events. The "current flow" creates the magnetic field.

I don't deny what you say is true, but they have no application in the issue we are discussing because there is no area of the solar atmosphere that is not experiencing "current flow". The sun spits out charged particles on a continuous basis as a result of the charge separation between the surface and the heliosphere. Really, Birkeland showed how all of this works empirically, in a lab, over 100 years ago. Look it up.
http://www.thesurfaceofthesun.com/birkeland.pdf

 

[Ziggurat]

In that case the "stored magnetic energy" you're talking about is kinetic energy in the one coil that is transferred to the secondary coil.

This is simply false, as even a little bit of consideration would demonstrate. The kinetic energy stored in a current depends upon the mass of the charge carriers. But the energy stored in the magnetic field is independent of the charge carrier mass: it would be the same if you fixed the electrons in place and moved the protons. Likewise, if we consider a fixed velocity for our charge carriers, the kinetic energy will scale linearly with the density of charge carriers. So will the current and the magnetic field. But the energy stored in the field scales as the square of the field, so it would scale as the square of the charge carrier density. Again, we see that it CANNOT be due to kinetic energy.

Energy is stored in the field itself. This energy is DIFFERENT from (and frequently many orders of magnitude larger than) the kinetic energy of the charge carriers. That is why calculating such energies requires only the current, not the charge carrier mass, velocity, or density. You have, in fact, failed a rather elementary and common electrodynamics question.