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VERSION:2.0
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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-3040
DTSTART:20130925T193000Z
DURATION:PT1H0M0S
DTSTAMP:20260317T062519Z
LAST-MODIFIED:20130919T133831Z
LOCATION:4274 Chamberlin Hall
SUMMARY:Cosmic Ray Diffusion in a Dynamic Milky Way: recovering the ob
 served B/C ratio in a spiral-armed cosmic ray propagation model\, NPAC
  (Nuclear/Particle/Astro/Cosmo) Forum\, David Benyamin\, Racah Institu
 te of Physics\, Hebrew University of Jerusalem
DESCRIPTION:We develop a fully three dimensional numerical code descri
 bing the diffusion of cosmic rays in the Milky Way. It includes the nu
 clear spallation chain up to Oxygen\, and allows the study of various 
 cosmic ray properties\, such as the CR age\, grammage traversed\, and 
 the ratio between secondary and primary particles. This code enables u
 s to explore a model in which a large fraction of the cosmic ray accel
 eration takes place in the vicinity of galactic spiral arms and that t
 hese spiral arms are dynamic.<br>
\n<br>
\nWe show that the effect of 
 having dynamic spiral arms is to limit the age of cosmic rays at low e
 nergies. This is because at low energies the time since the last spira
 l arm passage governs the Cosmic Ray (CR) age\, and not diffusion. Usi
 ng the model\, the observed spectral dependence of the secondary to pr
 imary ratio is recovered without requiring any further assumptions suc
 h as a galactic wind\, re-acceleration or various assumptions on the d
 iffusivity. In particular\, we obtain a secondary to primary ratio whi
 ch increases with energy below about 1 GeV.
URL:https://www.physics.wisc.edu/events/?id=3040
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