천문학회보 (The Bulletin of The Korean Astronomical Society)
- 제36권1호
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- Pages.45.1-45.1
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- 2011
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- 1226-2692(pISSN)
Re-acceleration of Nonthermal Particles at Weak Cosmological Shock Waves
- Kang, Hye-Sung (Pusan National University) ;
- Ryu, Dong-Su (Chungnam National University)
- 발행 : 2011.04.05
초록
Shock waves form in the intergalactic medium as a consequence of accretion, merger, and turbulent motion during the structure formation of the universe. They not only heat gas but also govern non-thermal processes through the acceleration of cosmic rays (CRs), production of magnetic fields, and generation of vorticity. We examine diffusive shock acceleration of the pre-existing as well as freshly injected populations of nonthermal, CR particles at weak cosmological shocks. Since the injection is extremely inefficient at weak shocks, the pre-existing CR population dominates over the injected population. If the pressure due to pre-existing CR protons is about 5 % of the gas thermal pressure in the upstream flow, the downstream CR pressure can absorb typically a few to 10 % of the shock ram pressure at shocks with the Mach number M<3. Yet, the re-acceleration of CR electrons can result in a substantial synchrotron emission behind the shock. The implication of our findings for observed bright radio relics is discussed.
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