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arXiv 1707.00262astro-ph.HE
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超新星遗迹中初级宇宙射线的异常分布作为随时间变化的粒子加速的证据

Anomalous distributions of primary cosmic rays as evidence for time-dependent particle acceleration in Supernova remnants

Yiran Zhang, Siming Liu, Qiang Yuan

摘要:

最近对宇宙线(CR)谱的精确测量表明,质子的能量分布比重核的能量分布更软,并且对于$\sim$ 200 GV以上的所有核成分都存在谱硬化。为这些异常提出的模型通常假设粒子加速过程的稳态解。我们表明,如果扩散系数有一个弱的依赖于超新星遗迹(SNR)的冲击波前附近的粒子刚性,随时间变化的线性扩散冲击波加速的解决方案在两个阶段的SNR演变可以自然地解释这些异常。CRs的高能量成分主要由自由膨胀和绝热阶段的加速和富集重元素以及高冲击速度所支配。低能量成分可能是由于在辐射相中具有低金属含量的致密分子云中传播的慢激波加速。随能量的增加,含时解的谱逐渐软化,而不是单一的幂律分布,这可能是CR的“膝”的原因。

英文摘要:

Recent precise measurements of cosmic ray (CR) spectra show that the energy distribution of protons is softer than those of heavier nuclei, and there are spectral hardenings for all nuclear compositions above $\sim$200 GV. Models proposed for these anomalies generally assume steady-state solutions of the particle acceleration process. We show that, if the diffusion coefficient has a weak dependence on the particle rigidity near shock fronts of supernova remnants (SNRs), time-dependent solutions of the linear diffusive shock acceleration at two stages of SNR evolution can naturally account for these anomalies. The high-energy component of CRs is dominated by acceleration in the free expansion and adiabatic phases with enriched heavy elements and a high shock speed. The low energy component may be attributed to acceleration by slow shocks propagating in dense molecular clouds with low metallicity in the radiative phase. Instead of a single power-law distribution, the spectra of time-dependent solutions soften gradually with the increase of energy, which may beresponsible for the "knee" of CRs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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