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Ryu, Dongsu
Astrophysics Lab
Research Interests
  • Shock waves and turbulence in clusters of galaxies
  • Origin and evolution of magnetic fields and cosmic rays in the universe
  • Plasma astrophysical phenomena in the large-scale structure of the universe

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Injection of kappa-like suprathermal particles into diffusive shock acceleration

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Title
Injection of kappa-like suprathermal particles into diffusive shock acceleration
Author
Kang, HyesungPetrosian, VaheRyu, DongsuJones, T. W.
Issue Date
2014-06
Publisher
IOP PUBLISHING LTD
Citation
ASTROPHYSICAL JOURNAL, v.788, no.2, pp.142
Abstract
We consider a phenomenological model for the thermal leakage injection in the diffusive shock acceleration (DSA) process, in which suprathermal protons and electrons near the shock transition zone are assumed to have the so-called κ-distributions produced by interactions of background thermal particles with pre-existing and/or self-excited plasma/MHD waves or turbulence. The κ-distribution has a power-law tail, instead of an exponential cutoff, well above the thermal peak momentum. So there are a larger number of potential seed particles with momentum, above that required for participation in the DSA process. As a result, the injection fraction for the κ-distribution depends on the shock Mach number much less severely compared to that for the Maxwellian distribution. Thus, the existence of κ-like suprathermal tails at shocks would ease the problem of extremely low injection fractions, especially for electrons and especially at weak shocks such as those found in the intracluster medium. We suggest that the injection fraction for protons ranges 10-4-10-3 for a κ-distribution with 10 ≲ κp ≲ 30 at quasi-parallel shocks, while the injection fraction for electrons becomes 10-6-10-5 for a κ-distribution with κe ≲ 2 at quasi-perpendicular shocks. For such κ values the ratio of cosmic ray (CR) electrons to protons naturally becomes K e/p ∼ 10-3-10 -2, which is required to explain the observed ratio for Galactic CRs.
URI
https://scholarworks.unist.ac.kr/handle/201301/5061
URL
http://iopscience.iop.org/article/10.1088/0004-637X/788/2/142/meta;jsessionid=F54347FC199170BC2437323D71D8ABDD.c4.iopscience.cld.iop.org
DOI
10.1088/0004-637X/788/2/142
ISSN
0004-637X
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