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Magnetic reconnection

  1. Dec 8, 2007 #1
    Is this effect real? as far as i've seen there has been no tests that would suggest that this can actually occur. It seems to be used a lot to exaplin various things in astronomy, but i have yet to see any experiment that verifys it is a real effect. There are many other effects to do with magnetism that seem dubious at best. Such as magnetic knots, open magnetic fields and magnetic cracks. Are there actually any observed and tested instances of these phenomenon? or are they more hypothesis than fact?

    I just find it hard to see how a metaphysical construct such as a magnetic filed line could reconnect or get tied into a 'knot'. In my mind there is clear difference between 1) conceptual constructs that are convenient tools for thinking about and visualizing a process, and 2) the physical process itself. The former (the concept) exists only in one’s mind. It does not exist in three-dimensional space. The latter (the process) concerns the movement or interaction of things that really do exist in our world.

    I noticed the wikipedia page does not cite any references on this subject; http://en.wikipedia.org/wiki/Magnetic_reconnection
     
  2. jcsd
  3. Dec 8, 2007 #2
    What is the current understanding of what magnetic reconnection actually does in space? I have read before it was used to explain sunspots and the heating of the corona. I have seen recently many models making use of Alfven waves, and many other magnetic based concpets to explain these outstanding problems in astrophysics, but I have read over twenty different theories for this problem, so i'm not sure which one is the most accepted of the lot. http://cluster.irfu.se/ks/bib/prl06corona.pdf

    http://www.holoscience.com/news.php?article=s9ke93mf

    Are there any experiments that verify these magnetic based ideas?


    p.s. This should probably be moved to cosmology or astrophysics.
     
    Last edited: Dec 9, 2007
  4. Jan 23, 2008 #3

    Nereid

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    Clicking on this link will take you to the Magnetic Reconnection Experiment, a research project within the Princeton Plasma Physics Laboratory.

    There's quite a bit to explore there; depending on what you've learned, so far, in physics, you might start with the "Physics" link (in the panel on the left), then "Results", followed by "Links" and "Publications".

    As you explore, drop back here with any questions you have. It would be helpful if you could also indicate the level of physics you are comfortable with, that way folk here can write answers to suit you.

    PS I think you'll find that many of the questions in your second post are also answered, at least partially. If you know how to do it, you might try to get hold of some relevant papers which may be published from last month's AGU meeting in San Francisco, particularly those by authors of the presentations and posters of the 40 Solar and Heliospheric Physics section sessions. As to moving this thread, or just the second post, this stuff isn't really astrophysics, if only because the phenomena are studied today more by in situ measurement than by remote sensing ('detection of photons'); this webpage gives a brief summary of what we might call the 'remote sensing' (or astronomical) era of the study of magnetospheric physics.
     
    Last edited: Jan 23, 2008
  5. Jan 23, 2008 #4

    Nereid

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    Moved, from General Physics.
     
  6. Jan 25, 2008 #5

    Nereid

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    I found the lecture notes used in a graduate course in plasma physics, online:
    The source is, per the HTML version, "Richard Fitzpatrick, Associate Professor of Physics, The University of Texas at Austin", and is dated 2006.

    The university website says this about him:
    PlasmaSphere, if you're still reading this thread (or if you even visit PF any more), this lecture course presents the context of "magnetic reconnection" - within MHD, which is a plasma fluid theory.

    In particular, in relation to the key part of your OP1, I think you'll find, if you read these lecture notes and follow them well enough, that the relationship between 'metaphysical construct', 'conceptual constructs', 'process', 'the physical process itself', and 'things that really do exist in our world' is considerably more complex and nuanced than the worldview your OP seems to reflect.

    1 "I just find it hard to see how a metaphysical construct such as a magnetic filed line could reconnect or get tied into a 'knot'. In my mind there is clear difference between 1) conceptual constructs that are convenient tools for thinking about and visualizing a process, and 2) the physical process itself. The former (the concept) exists only in one’s mind. It does not exist in three-dimensional space. The latter (the process) concerns the movement or interaction of things that really do exist in our world."
     
  7. Jan 26, 2008 #6
    What would Maxwell make of all this reconnection melarchy then? I dont think he would like his most fundamental properties of magnetism to be changed to account for this energy we observe being released. Surely there has to be a more likely explanation than one that changes something as well established as the laws of magnetism?

    Heres and animation of roughly what is claimed to be occuring in magnetic reconnection; http://sci.esa.int/science-e-media/img/5f/Animation-4_195.gif ( i dont think i can attatch it here for some reason? )

    They are quite literally trying to claim that magnetic field lines make and break connection and thereby release energy. Magnetic fields do not do that. They only form as a full continuum and they can't make and break connections like electrical circuits. They are mistaken in their basis premise which is why Alfven himself ridiculed the idea. The worst part in my opinion is they keep trying to use MHD theory to support this idea, even though Alfven publicly rejected the idea.

    The father of MHD theory claimed it was false. Now they turn right around and try to use MHD theory to support the idea using *uncontrolled* observations from space, and have not demonstrated this reconnection actually occuring in a lab.

    Dont get me wrong, there obviously is a phenomenon that is creating the energy observed in the various experiments you provided me with Neried, I just dispute that it has anything to do with 'magnetic reconnection' as such. Once i see the actual data from experiments that clearly shows the magnetic field lines reconnecting, not the just the mathematics of the theory, i will reconsider my opinion. So far i have not.

    http://members.cox.net/dascott3/IEEE-TransPlasmaSci-Scott-Aug2007.pdf
    Maybe the process attributed to magnetic reconnection is infact a variant of the slightly more established Z-pinch or magnetic confinement techniques achieved in various other experiments.
     
    Last edited: Jan 26, 2008
  8. Jan 26, 2008 #7
    Pre-Graduate, second year of straight physics course, if thats going to help anything
     
    Last edited: Jan 26, 2008
  9. Jan 26, 2008 #8
    The main difference is that if magnetic fields can not be open ended (as maxwells equations certainly imply) that should mean that these magnetic fields are connecting stellar bodies through the IPM, which gives quite a different idea than the conventional approach that the magnetic field lines end on intermolecular clouds. This connection between stars is what is currently most astronomers seem unwilling to accept, and so because of this have to postulate that magnetic fields are open and do not connect between bodies in space. However Alfven et al didn't see the sun as a closed system, that makes a big difference in how one looks at the universe.

    Many facile observations to the contrary indicate that this is likely not the case, and the IPN contains much more EM activity, and connections between interstellar bodies, than previously realized.

    The reason i say this is that all astronomers now know that the magnetospheres of planets have depressions above the poles where the electric currents from the sun gain entry into the upper atmosphere, and create the aurora's. Using this fact it is common sense to suggest that since the sun also has similar magnetic poles just like every other planet, these depressions on the suns poles are also where the electric currents enter the sun, from the galaxy.

    http://www.dailygalaxy.com/my_weblog/2007/12/massive-magneti.html
    The report discusses the THEMIS spacecraft's recent observations of "giant magnetic ropes that connect Earth's upper atmosphere to the Sun and explosions in the outskirts of Earth's magnetic field." Describing the THEMIS encounter with a "magnetic rope" NASA investigator Dave Sibeck states: "It was very large, about as wide as Earth, and located approximately 40,000 miles above Earth's surface in a region called the magnetosphere." Investigators observed that the so-called rope "formed and unraveled in just a few minutes, providing a brief but significant conduit for solar wind energy. Other ropes quickly followed: 'They seem to occur all the time,' says Sibeck."

    Magnetic "ropes"? NASA scientists often use the phrase "flux ropes" to describe these twisted filamentary pathways traversed by charged particles. Maybe i'm missing something here, but would not Birkeland currents be a more correct name to attribute to the 'twisting filaments'?

    To me the rope-like structure is not a curiosity; it is the structure taken by current flow due to the long-range attraction and short-range repulsion between current filaments. The "twisted magnetic fields" are simply the signature of the electric current flow. These entwined plasma filaments act as transmission lines carrying "field-aligned" currents across interplanetary and interstellar space. http://en.wikipedia.org/wiki/Birkeland_current


    Surely, it is quite logical to assert that this same process could be connecting the sun electromagnetically to the rest of the galaxy? If this is not so, why?
     
    Last edited: Jan 26, 2008
  10. Feb 8, 2008 #9

    Nereid

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    PS, I think your confusion can be traced fairly easily to misunderstandings over what the scope of plasma physics is.

    The behaviour of real plasmas is impossible to describe in closed analytic forms that are also soluble (except, as usual, in highly restricted cases that are essentially unrealistic).

    So plasma physics involves making assumptions pertinent to the plasma regime of interest, and proceeding to describe expected behaviour in a form sufficiently simple as to permit comparison with experimental or observational results.

    Have you had a chance to read some of the Fitzpatrick lecture notes that I provided a link to? If so, you'll have seen how this assumption/approximation approach works, in many ways - look at the introduction to the section on MHD theory, for example.
    That's easy - once he understood that charges are quantized (electrons, ions, and in some cases positrons), he'd have quickly appreciated the challenges of applying 'his' equations to trying to solve for the behaviour of real plasmas in closed analytic forms. It may have taken him a bit longer to appreciate the ingenuity of some of the modern plasma models, and perhaps quite a bit longer to understand how electromagnetism was reformulated in terms of 20th century physics (i.e. incorporating quantum mechanics and relativity).
    This is a particularly good example of your misunderstanding ... first, no one "owns" scientific theories, so an appeal to authority (Alfvén's, in this case) is illegitimate as science; second, you present a poor word sketch as a substitute for the classes of plasma models in which 'magnetic reconnection' is being used, and an inaccurate one at that.

    If you'd like help in understanding what 'magnetic reconnection' means, in terms of the classes of plasma models in which it is used, and what the underlying assumptions are, just ask. But please, do not make bald assertions unsubstantiated by the relevant physics.
    Well, I don't think that you will ever see any such thing ... the electrons and ions do their things regardless of what any physicist thinks. Further, the plasma physics we are discussing here is, even in the most general sense, only a (classical physics) limiting case of how you *should* describe plasmas, if you wanted to be as complete as possible - you need to use the full force of QED if you insist on that.

    But how about this: you pick one of the 'magnetic reconnection' papers, preferably a lab experiment one, and we can go through the physics in it, to learn about assumptions and approximations.
    Perhaps - you pick a paper, and we'll find out, eh?

    Oh, and BTW, please do not cite Scott as a reference ... except if you wish to have a discussion of how badly he misunderstands the very physics he claims to be talking about.
     
  11. Feb 8, 2008 #10

    Nereid

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    Back in the S&D thread, in which you made some posts, the topic of the legitimacy of press releases (and blogs) was discussed, particularly in terms of their legitimacy as relevant inputs to the sections of PF where the actual physics is discussed. It was made clear - I hope - that they are not to be used, and certainly not on their own.

    This post of yours that I am quoting contains - as far as I can see - no physics beyond word sketches. That's not how things work here in Physics Forums; you need to get to the physics used by the relevant researchers.

    To your questions.

    The best way to address them is to discuss the underlying physics, perhaps starting with that used by the THEMIS team and as (no doubt) clearly laid out in the relevant papers they have published. An alternative might be to start with the relevant part of the Fitzpatrick lectures. Which would you prefer?

    In any case, please do not continue to post material in the sections of PF devoted to physics that are little more than bald assertions based on nothing more than misunderstandings of press releases.
     
  12. Mar 2, 2008 #11
    Just though i would say I have not forgotten this conversation Neried, to be continued when I have more time. Maybe eventually we can reach a consensus on these new properties of magnetism in the cosmos.

    And out of interest, one quick question, what, scientifically speaking, are your objections to Scotts peer reviewed paper that I cited above in post #6?
     
  13. Mar 4, 2008 #12

    Astronuc

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    On what basis does one claim reconnection is melarchy?


    From the wikipedia article - a reference which is an entire textbook!
    Eric Priest, Terry Forbes, Magnetic Reconnection, Cambridge University Press 2000, ISBN 0521481791, contents and sample chapter online
     
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