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Post Info TOPIC: Galaxy magnetic field


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Intergalactic magnetic fields
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How did the universe get its magnetism?

How the universe got its magnetism? For long, it has been a mystery. Now, physicists claim to have attempted to solve it by using laser to create magnetic fields similar to those involved in formation of the first galaxies.
Magnetic fields exist throughout galactic and intergalactic space, what is puzzling is how they were created originally and how they became so strong.

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RE: Galactic Magnetic Fields
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Magnetic fields set the stage for the birth of new stars

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. The work will be published in the November 24 edition of the journal Nature.
Astronomers know quite a bit about these so-called molecular clouds: They consist mainly of hydrogen molecules - unusual in a cosmos where conditions are rarely right for hydrogen atoms to bond together into molecules. And if one traces the distribution of clouds in a spiral galaxy like our own Milky Way galaxy, one finds that they are lined up along the spiral arms.
But how do those clouds come into being? What makes matter congregate in regions a hundred or even a thousand times more dense than the surrounding interstellar gas?
One candidate mechanism involves the galaxy's magnetic fields.

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Weak magnetic fields are "roaming" across the universe, according to a new study that may have solved the mystery of where the huge magnetic fields around galaxies come from.
Galaxies such as our Milky Way have their own large-scale magnetic fields. Although these fields are weak compared to planetary fields, scientists think the galactic versions help establish rates of star formation, guide cosmic rays, and regulate the dynamics of interstellar gas.
Most scientists believe the stronger magnetic fields of today's adult galaxies grew from weaker "seed" fields. But it's unclear where these older fields originated.
The two leading theories: The seed fields were created by the movement of charged gas in protogalaxies, or they were produced outside of galaxies by some unseen processes in the early universe.
New observations made with NASA's Fermi Gamma-ray Space Telescope support the idea that the seeds were there all along, even before galaxies themselves.

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Title: The Origin of Magnetic Fields in Galaxies
Authors: Rafael da Silva de Souza, Reuven Opher

Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We showed that the natural plasma fluctuations in the primordial universe, produces random dipole magnetic fields of comoving size ~1 pc and intensity ~ 0.1 \mu G at a redshift z ~ 10. The theory predicts an average magnetic field ~ 0.003 ~ nG over a 2 kpc region at z ~ 10. We assume this seed field and examine its amplification by a turbulent dynamo in a protogalaxy.
Whereas the standard \alpha-\Omega dynamo for a typical disk galaxy creates only a 2 e-fold amplification of the field in ~ 10^{9} years, the turbulent dynamo has a much shorter amplification time. Starting with the average seed magnetic field of B ~ 0.003 nG over ~ 2 kpc at z = 10, we find that in 10^{9} years, B is amplified to ~ 1 nG. This corresponds to a ~ 6 e-fold amplification of the field. In the process of collapsing to form galaxies at z ~10, the plasma density rises by a factor of ~ 200 and the magnetic fields, by a factor of ~ 34. Thus, 0.03 \mu G fields over 0.34 kpc regions in galaxies are predicted. If the dipole magnetic fields predicted by the Fluctuation-Dissipation-Theorem are not completely random, microgauss fields over regions \gtrsim 0.34 kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in \lesssim 10^{9} years in high redshift galaxies.

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Galaxy magnetic field
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U.S. astronomers using the world's largest fully steerable radio telescope have obtained the first direct measurement of a nascent galaxy's magnetic field.
Astronomers led by Professor Arthur Wolfe of the University of California-San Diego said the measurement of the magnetic field was as it appeared 6.5 billion years ago and is at least 10 times greater than the average value in the Milky Way.

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