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Cosmic bullets as particle accelerators and radio sourcesWe have simulated in two dimensions the dynamical evolution of dense gas clouds(`cosmic bullets') moving supersonically through a uniform low-density medium. The diffusive shock acceleration of relativistic protons (cosmic rays) and their dynamical feedback on the background flow are included by the two-fluid model for this process. The acceleration of relativistic electrons is approximated by a test-particle model, and a passive magnetic field is followed by a simple advection scheme. Strong bow shocks, with Mach numbers similar to that of a bullet's motion, are the most important particle accelerators in the flow, while tail shocks and shocks inside the bullets do not play generally significant roles in this regard. For our simulation parameters, approximately greater than 10% of the initial bullet kinetic energy is converted to a combination of internal energy of gas and cosmic-ray protons by the time the bullets begin to be disrupted. Characteristically, the cosmic rays gain several percent of the available kinetic energy. Bullet destruction on timescales only a little larger than the ram pressure bullet crushing time begins in response to Kelvin-Helmholtz and especially to Rayleigh-Taylor instabilities along the forward bullet surface. For dense bullets this happens before the bullet is stopped by ram pressure. According to our simple model for synchrotron emission from relativistic electrons accelerated and transported within the flows, that emission increases rapidly as the bullet begins to fragment, when it is strongly dominated by field enhancement in sheared flows. Synchrotron emission from the acceleration region within the bow shock is, by contrast, much weaker.
Document ID
19950040769
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Jones, T. W.
(Minnesota Univ. Minneapolis, MN, United States)
Kang, Hyesung
(Pusan National Univ. Pusan, Republic Of Korea)
Tregillis, I. L.
(Minnesota Univ. Minneapolis, MN, United States)
Date Acquired
August 16, 2013
Publication Date
September 1, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 432
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A72368
Funding Number(s)
CONTRACT_GRANT: NAGW-2548
CONTRACT_GRANT: NSF AST-91-00486
Distribution Limits
Public
Copyright
Other

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