TWO-STEP ACCELERATION MODEL OF COSMIC RAYS AT MIDDLE-AGED SUPERNOVA REMNANTS: UNIVERSALITY IN SECONDARY SHOCKS
- Division of Theoretical Astronomy, National Astronomical Observatory of Japan, Osawa, Mitaka 181-8588 (Japan)
- Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Sagamihara 229-8558 (Japan)
- Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)
Recent gamma-ray observations of middle-aged supernova remnants revealed a mysterious broken power-law spectrum. Using three-dimensional magnetohydrodynamic simulations, we show that the interaction between a supernova blast wave and interstellar clouds formed by thermal instability generates multiple reflected shocks. The typical Mach numbers of the reflected shocks are shown to be M{approx_equal} 2 depending on the density contrast between the diffuse intercloud gas and clouds. These secondary shocks can further energize cosmic-ray particles originally accelerated at the blast-wave shock. This 'two-step' acceleration scenario reproduces the observed gamma-ray spectrum and predicts the high-energy spectral index ranging approximately from 3 to 4.
- OSTI ID:
- 21452701
- Journal Information:
- Astrophysical Journal Letters, Vol. 723, Issue 1; Other Information: DOI: 10.1088/2041-8205/723/1/L108; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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