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Ryu, Dongsu
Astrophysics Lab
Research Interests
  • Shock waves and turbulence in clusters of galaxies

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DIFFUSIVE SHOCK ACCELERATION AT COSMOLOGICAL SHOCK WAVES

Cited 10 times inthomson ciCited 8 times inthomson ci
Title
DIFFUSIVE SHOCK ACCELERATION AT COSMOLOGICAL SHOCK WAVES
Author
Kang, HyesungRyu, Dongsu
Keywords
acceleration of particles; cosmic rays; galaxies: clusters: general; shock waves
Issue Date
201302
Publisher
IOP PUBLISHING LTD
Citation
ASTROPHYSICAL JOURNAL, v.764, no.1, pp.1 - 9
Abstract
We reexamine nonlinear diffusive shock acceleration (DSA) at cosmological shocks in the large-scale structure of the universe, incorporating wave-particle interactions that are expected to operate in collisionless shocks. Adopting simple phenomenological models for magnetic field amplification (MFA) by cosmic-ray (CR) streaming instabilities and Alfvenic drift, we perform kinetic DSA simulations for a wide range of sonic and Alfvenic Mach numbers and evaluate the CR injection fraction and acceleration efficiency. In our DSA model, the CR acceleration efficiency is determined mainly by the sonic Mach number Ms , while the MFA factor depends on the Alfvenic Mach number and the degree of shock modification by CRs. We show that at strong CR modified shocks, if scattering centers drift with an effective Alfven speed in the amplified magnetic field, the CR energy spectrum is steepened and the acceleration efficiency is reduced significantly, compared to the cases without such effects. As a result, the postshock CR pressure saturates roughly at ∼20% of the shock ram pressure for strong shocks with Ms ≳ 10. In the test-particle regime (Ms ≲ 3), it is expected that the magnetic field is not amplified and the Alfvenic drift effects are insignificant, although relevant plasma physical processes at low Mach number shocks remain largely uncertain.
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DOI
http://dx.doi.org/10.1088/0004-637X/764/1/95
ISSN
0004-637X
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SNS_Journal Papers
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