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Breaking Magnetic Field Lines

  1. Oct 11, 2012 #1
    When people talk about sunspots and the solar cycle and stuff like that, they often mention magnetic field lines poking through the surface of the sun. I'm pretty sure I get why the magnetic field lines would be twisted up by the non-uniform rotation of the sun, and why they would poke out of the surface.

    What I totally *do not* get, is how the heck a magnetic field line *breaks*. This seems to me that it would mean that magnetic field lines are physical things... or rather that they are "made of something", like some kind of material.

    I just don't have any sort of idea of how a magnetic field line could be broken based on my understanding of what a field line is. Is this something that I will learn about in E&M courses?
     
  2. jcsd
  3. Oct 11, 2012 #2

    Bobbywhy

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    Gold Member

    SHISHKABOB, You may learn about the “breaking” and "reconnecting" of magnetic lines here:

    “Magnetic reconnection (henceforth called "reconnection") refers to the breaking and reconnecting of oppositely directed magnetic field lines in a plasma. In the process, magnetic field energy is converted to plasma kinetic and thermal energy.”
    http://mrx.pppl.gov/Physics/physics.html

    For a real-life experiment see:
    “The Magnetic Reconnection Experiment”
    http://mrx.pppl.gov/

    For a site that uses great graphics to explain the process see:
    http://www.aldebaran.cz/astrofyzika/plazma/reconnection_en.html

    Finally, see our old friend (and the references at the bottom) Wikipedia:
    http://en.wikipedia.org/wiki/Magnetic_reconnection

    Cheers,
    Bobbywhy
     
    Last edited: Oct 11, 2012
  4. Oct 11, 2012 #3
    thanks, can't believe I didn't think of looking on wikipedia >.>
     
  5. Oct 12, 2012 #4
    Very interesting plasma physics phenomenon. Astounded though at the widespread and officially sanctioned use of terminology that implies a failure of one of the four Maxwell eqn's: ∇.B = 0. That eq'n, which in effect states magnetic monopoles do not exist, guarantees there can be no such thing as an 'open field line'. Yet that terminology is used in describing line configurations in third illustration at http://www.aldebaran.cz/astrofyzika/plazma/reconnection_en.html (3rd link given in #2). Generally, 'reconnection of field lines' implies they can have 'loose ends' which is a violation of ∇.B = 0. So what actually happens is the plasma as current source reconfigures in such a way that magnetic field lines, which always form closed loops, reconfigures to give the appearance of 'breaking' and 'reattaching' of such lines. This is just a vector summation situation and at no space-time region will there be lines that are not continuous. Disappointing that none of those articles linked in #2 make the point that ∇.B = 0 is not being violated.
     
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