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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-1748
DTSTART:20100112T213000Z
DTEND:20100112T231000Z
DTSTAMP:20260506T161430Z
LAST-MODIFIED:20100114T205956Z
LOCATION:3425 Sterling Hall
SUMMARY:Magnetic Fields in the Cosmic-ray modified shocks\, Astronomy 
 Colloquium\, Andrey Beresynak\, UW Madison Astronomy
DESCRIPTION:We propose a model for Diffusive Shock Acceleration (DSA) 
 in which<br>
\nstochastic magnetic fields in the shock precursor are g
 enerated<br>
\nthrough purely fluid mechanisms of a so-called small-sc
 ale dynamo.<br>
\nThis contrasts with previous DSA models that conside
 red magnetic<br>
\nfields amplified through cosmic ray streaming insta
 bilities\; i.e.\,<br>
\neither by way of individual particles resonant
  scattering in the<br>
\nmagnetic fields\, or by macroscopic electric 
 currents associated with large-scale cosmic ray streaming.  In our pic
 ture\, the solenoidal velocity perturbations that amplify magnetic fie
 lds are produced through the interactions of the pressure gradient of 
 the cosmic ray precursor and density inhomogeneities in the inflowing 
 fluid.<br>
\nOur estimates show that this mechanism provides fairly fa
 st<br><br>
\ngrowth of magnetic field and is very generic. For superno
 vae shocks this mechanism is capable of generating upstream magnetic f
 ields that are sufficiently strong for accelerating cosmic rays up to 
 around $10^{16}$ eV.<br><br>
\n
URL:https://www.physics.wisc.edu/events/?id=1748
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