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arXiv 2103.02375astro-ph.HE
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来自超新星遗迹的Cosmic ray质子和电子

Cosmic ray protons and electrons from supernova remnants

P. Cristofari, P. Blasi, D. Caprioli

摘要:

超新星遗迹在整个演化过程中释放的宇宙射线质子和电子的光谱知之甚少,因为很难解释激波前沿下游的粒子逃逸和约束,那里存在绝热和辐射损失。在这里,我们计算宇宙射线质子的光谱不同类型的超新星的演化过程中释放,占逃逸从上游和绝热损失的粒子平流下游的冲击和解放在以后的时间。同样的计算也适用于电子。通过对非共振和共振流动不稳定性及其饱和引起的磁场放大的解析处理,计算了激波后区域的磁场。我们发现,当场是宇宙射线驱动的非共振不稳定性单独增长的结果时,超新星遗迹释放的电子和质子的光谱确实是不同的,但这种差异只有在能量为$\gtrsim 100-1000$ GeV时才变得明显,而电子光谱的观测需要在能量低至$\sim 10$ GeV时存在这种差异。在如此低的能量下,超新星遗迹演化的后期阶段(激波速度$\ll 1000$ km/s)需要大量的磁场放大,这可能不是由于流动不稳定性,而是流体动力学过程。我们评论这种条件的可行性,并推测的可能性,即电子和质子之间的光谱形状的差异可能反映了一些未知的加速效应,或额外的能量损失的茧周围的来源。

英文摘要:

The spectrum of cosmic ray protons and electrons released by supernova remnants throughout their evolution is poorly known, because of the difficulty in accounting for particle escape and confinement in the downstream of a shock front, where both adiabatic and radiative losses are present. Here we calculate the spectrum of cosmic ray protons released during the evolution of supernovae of different types, accounting for the escape from upstream and for adiabatic losses of particles advected downstream of the shock and liberated at later times. The same calculation is carried out for electrons. The magnetic field in the post-shock region is calculated by using an analytic treatment of the magnetic field amplification due to non--resonant and resonant streaming instability and their saturation. We find that when the field is the result of the growth of the cosmic-ray--driven non--resonant instability alone, the spectrum of electrons and protons released by a supernova remnant are indeed different, but such a difference becomes appreciable only at energies $\gtrsim 100-1000$ GeV, while observations of the electron spectrum require such a difference to be present at energies as low as $\sim 10$ GeV. An effect at such low energies requires substantial magnetic field amplification in the late stages of the supernova remnant evolution (shock velocity $\ll 1000$ km/s), perhaps not due to streaming instability but hydrodynamical processes. We comment on the feasibility of such conditions and speculate on the possibility that the difference in spectral shape between electrons and protons may reflect either some unknown acceleration effect, or additional energy losses in cocoons around the sources.

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