Diffusion of cosmic rays in a multiphase interstellar medium swept-up by a supernova remnant blast wave

作者：Roh Soonyoung^*; Inutsuka Shu ichiro; Inoue Tsuyoshi

来源：Astroparticle Physics, 2016, 73: 1-7.

DOI：10.1016/j.astropartphys.2015.06.001

• Bohm diffusion
• Galactic cosmic rays
• Superdiffusion
• Supernova remnant

Supernova remnants (SNRs) are one of the most energetic astrophysical events and are thought to be the dominant source of Galactic cosmic rays (CRs). A recent report on observations from the Fermi satellite has shown a signature of pion decay in the gamma-ray spectra of SNRs. This provides strong evidence that high-energy protons are accelerated in SNRs. The actual gamma-ray emission from pion decay should depend on the diffusion of CRs in the interstellar medium. In order to quantitatively analyse the diffusion of high-energy CRs from acceleration sites, we have performed test particle numerical simulations of CR protons using a three-dimensional magnetohydrodynamics (MHD) simulation of an interstellar medium swept-up by a blast wave. We analyse the diffusion of CRs at a length scale of order a few pc in our simulated SNR, and find the diffusion of CRs is precisely described by a Bohm diffusion, which is required for efficient acceleration at least for particles with energies above 30 TeV for a realistic interstellar medium. Although we find the possibility of a superdiffusive process (travel distance alpha t(0.75)) in our simulations, its effect on CR diffusion at the length scale of the turbulence in the SNR is limited.

• 出版日期2016-1
• 单位中国科学院国家天文台