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CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3080
DTSTART:20130926T203000Z
DTEND:20130926T220000Z
DTSTAMP:20260419T211922Z
LAST-MODIFIED:20130911T202101Z
LOCATION:4421 Sterling Hall
SUMMARY:Cosmic magnetogenesis: From spontaneously emitted aperiodic tu
 rbulent to ordered equipartition fields\, Astronomy Colloquium\, Reinh
 ard Schlickeiser\, Ruhr-University Bochum\, Germany
DESCRIPTION:<br>
\nNonmagnetized fully-ionized plasmas spontaneously e
 mit aperiodic turbulent magnetic field fluctuations. Its fluctuation i
 ntensities are dominated by the contribution from a recently found col
 lective\, damped mode\, which modifies the earlier estimate of the tot
 al magnetic field strength to $|delta B|=24beta _e^{1/4}(gn_em_ec^2)^{
 1/2}$ G in the case of no collisional damping\, where $g$ denotes the 
 plasma parameter\, $beta _e$ the thermal electron velocity in units of
  $c$ and $n_e$ the electron density. Accounting for simultaneous visco
 us damping reduces the estimate to $|delta B|=2305g(n_em_ec^2)^{1/2}$ 
 G. For the unmagnetized intergalactic medium\, immediately after the r
 eionization onset\, the field strengths from this mechanism are about 
 $6.8cdot 10^{-13}$ G for no collisional damping and $1.5cdot 10^{-16}$
  G for viscous damping. Maximum spatial scales of $10^{15}$ cm of the 
 emitted aperiodic fluctuations are possible. These guaranteed magnetic
  fields in the form of randomly distributed fluctuations\, produced by
  the spontaneous emission of the isotropic\, thermal IGM plasma\, may 
 serve as seed fields for possible amplification by later possible plas
 ma instabilities from anisotropic plasma particle distributions functi
 ons\, MHD instabilities and/or the MHD dynamo process. Because of the 
 high turbulent plasma beta\, the seed fields are tied passively to the
  highly conducting IGM plasma as frozen-in magnetic fluxes\, and there
 fore are subject to subsequent hydrodynamical shear or compression of 
 the IGM medium from the shock waves of the supernova explosions of the
  first stars at the end of their lifetimes\, or from supersonic stella
 r and galactic winds.<br>
\n
URL:https://www.physics.wisc.edu/events/?id=3080
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