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Magnetic feilds in space

  1. Oct 18, 2011 #1
    With modern telescopes we can see magnetic fields throughout the universe, in our solar system, in and around galaxies and in interstellar space. Given that magnetic fields do not exist without moving charge i.e. a electric current.Why is it that;
    a) Astrophysics only ever talk about magnetic fields and never seem to mention the electric currents that must produce them
    b) Why these electric currents/magnetic fields when they obviously exist throughout the universe are not considered in celestial mechanics.
     
  2. jcsd
  3. Oct 18, 2011 #2

    phyzguy

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    The empty space between stars and galaxies is not empty, but is filled with low-density ionized gas, which is also known as plasma. The motion of the charged particles in the plasma creates electric currents, which is what sustains the magnetic fields. The motion of the plasma is described by the equations of magnetohydrodynamics (MHD). Below are some links to get you started.

    http://en.wikipedia.org/wiki/Astrophysical_plasma
    http://en.wikipedia.org/wiki/Interstellar_medium
    http://en.wikipedia.org/wiki/Magnetohydrodynamics

    For most problems in celestial mechanics, the electromagnetic forces are negligible compared to the gravitational forces, so the EM forces are ignored. However, in some cases, such as neutron stars, black hole accretion disks, gamma-ray bursts, etc., it is believed that the magnetic fields play a dominant role, and there are many people studying the magnetic field behavior in detail.
     
  4. Oct 19, 2011 #3
    They do. Plasma and magetodynamics.

    They are for small objects like asteroids and spacecraft (through radiation pressure). The problem is that a large object produces more gravity so that if you estimate the impact that a magnetic field has on say Jupiter, then it turns out to be ignorable.
     
  5. Nov 24, 2011 #4

    Dotini

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    Apparently there is still some debate on how magnetic fields impose direction upon molecular clouds (stellar nurseries). Some new research is reported by the journal Nature.

    http://www.nature.com/nature/journal/v479/n7374/full/nature10551.html?WT.ec_id=NATURE-20111124
    The formation of molecular clouds, which serve as stellar nurseries in galaxies, is poorly understood. A class of cloud formation models suggests that a large-scale galactic magnetic field is irrelevant at the scale of individual clouds, because the turbulence and rotation of a cloud may randomize the orientation of its magnetic field1, 2. Alternatively, galactic fields could be strong enough to impose their direction upon individual clouds3, 4, thereby regulating cloud accumulation and fragmentation5, and affecting the rate and efficiency of star formation6. Our location in the disk of the Galaxy makes an assessment of the situation difficult. Here we report observations of the magnetic field orientation of six giant molecular cloud complexes in the nearby, almost face-on, galaxy M33. The fields are aligned with the spiral arms, suggesting that the large-scale field in M33 anchors the clouds.


    http://www.sciencedaily.com/releases/2011/11/111116132119.htm
    Astronomers at the Max Planck Institute for Astronomy have, for the first time, measured the alignment of magnetic fields in gigantic clouds of gas and dust in a distant galaxy. Their results suggest that such magnetic fields play a key role in channeling matter to form denser clouds, and thus in setting the stage for the birth of new stars.


    Respectfully submitted,
    Steve


    Edit: Link to the Nature PDF: http://arxiv.org/abs/1111.2745
     
    Last edited by a moderator: May 5, 2017
  6. Dec 7, 2011 #5
    "Given that magnetic fields do not exist without moving charge i.e. a electric current.Why is it that;
    a) Astrophysics only ever talk about magnetic fields and never seem to mention the electric currents that must produce them
    b) Why these electric currents/magnetic fields when they obviously exist throughout the universe are not considered in celestial mechanics."

    Additionally interstellar and intergalactic primary and secondary cosmic ray fluxes provide a cascade of many and mainly positively charged particles. Even though interstellar and intergalactic space is not energetically closed; if you throw a huge Gaussian sphere in the center of a void; you'd expect typically a reciprocal isotropic and homogeneous flux through all segments of the surface. Only two "oh my god particles" colliding head on result in a cascade of billions of charge particles: i.e. millions of charged and neutral pions and kaons, decaying into positrons, electrons, muons, neutrinos, gamma rays etc. Within the Gaussian sphere the energy and or matter remains... Wimps, fields, etc.

    The main idea is energy/matter is conserve as the flux continues until in one cup full of baryonically empty vacuum, you have enought energy to boil every ocean on earth.

    quantum field theory and dark energy predictions show the energy exist.

    Well this is my take.

    Respectfully

    Mr. Zagoni
     
  7. Jan 26, 2012 #6

    Dotini

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    Gold Member

    http://www.physorg.com/news/2012-01-galactic-magnetic-field-lab-bolsters.html
    "According to our previous understanding, any magnetic field that had been made ought to have gone away by now," said Paul Drake, the Henry S. Carhart Collegiate Professor of Atmospheric, Oceanic, and Space Sciences and a professor in physics at U-M. "We didn't understand what mechanism might create a magnetic field, and even if it happened, we didn't understand why the magnetic field is still there.

    "It has been a very enduring mystery."

    Discovered by a German astronomer in1950, the Biermann process predicts that a magnetic field can spring up spontaneously from nothing more than the motion of charged particles. Plasma, or charged particle gas, is abundant in space.

    Scientists believe that large clouds of gas collapsing into galaxies sent elliptically shaped bubbles of shockwaves through the early universe, touching off flows of electric current in the plasma of the intergalactic medium.


    Respectfully submitted,
    Steve
     
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