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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-8456
DTSTART:20231026T203000Z
DTEND:20231026T213000Z
DTSTAMP:20260414T050617Z
LAST-MODIFIED:20231011T121451Z
LOCATION:4421 Sterling Hall
SUMMARY:Cosmic ray electron re-acceleration in the intracluster medium
  via magnetic pumping\, Astronomy Colloquium\, Aaron Tran\, UW-Madison
DESCRIPTION:Clusters of galaxies are embedded in a hot (T~10^7 K)\, lo
 w-density halo of gas called the intracluster medium (ICM).  In some 
 clusters\, the ICM hosts low-frequency (MHz–GHz) radio synchrotron e
 mission associated with radio galaxies\, jets\, and cluster merger-ind
 uced shocks and turbulence.  The radio emission comes from GeV cosmic
  ray electrons (CRe).  Some CRe may be "fossils"\, i.e.\, previously-
 accelerated CRe that then radiated and cooled to long-lived MeV energi
 es.  Fossil CRe are invisible until some perturbation\, like adiabati
 c compression or turbulence\, re-accelerates the CRe back to GeV energ
 ies.  I will present a recent study of CRe re-acceleration via magnet
 ic pumping\, a mechanism in which small-scale (nanoparsec) plasma wave
 s coupled to large-scale (kiloparsec to Megaparsec) motions can effici
 ently energize CRe.  In 1D kinetic plasma simulations\, we show that 
 ion cyclotron wave scattering with background compression leads to res
 onant CRe gaining ~10-30% of their initial energy in one compress/expa
 nd cycle\, assuming adiabatic expansion without further scattering.  
 I will comment briefly on the applicability and limitations of this re
 -acceleration mechanism\, and on prospects for future work.
URL:https://www.physics.wisc.edu/events/?id=8456
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