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arXiv 1707.00525astro-ph.HE
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关于宇宙射线中稳定次级核的谱

On the spectrum of stable secondary nuclei in cosmic rays

Pasquale Blasi

摘要:

宇宙射线中次级核和初级核的通量之比,长期以来一直被用作宇宙射线粒子在整个银河系旅行中所经过的克重的指标。基本的想法是,初级粒子在天体物理源中被加速,例如超新星遗迹激波,最终在银河系体积中传播,偶尔与气体相互作用,主要是在银河系的圆盘中,在那里,它们通过spectrometry产生次级核。在足够高的能量下,通常是$\gtrsim 100$ GeV/n,次级核与主初级核的通量之比被发现以$E_{k}^{-δ}$为尺度,其中$E_{k}$是每个核子的能量(自旋反应中的守恒量),$δ$确定扩散系数的能量依赖性。可能首先导致宇宙射线加速的同一冲击波也会在上游拾取任何其他带电粒子,只要它们高于注入的阈值。在星际介质中由中子产生的次级核也不例外,因此它们也会被加速。这种影响是不可避免的,只是其强度可能是有争议的。我们计算光谱的二次元素,如硼和锂,考虑到冲击再加速,并比较我们的预测与最近的观察B/C比和初步测量的硼和锂通量。这两组数据似乎证实了次级核的再加速确实起着重要作用,从而影响了宇宙射线物理学中经常使用的那些标度规则的有效性。

英文摘要:

The ratio of the fluxes of secondary and primary nuclei in cosmic rays has long been used as an indicator of the grammage traversed in the journey of cosmic ray particles throughout the Galaxy. The basic idea is that primary particles are accelerated in astrophysical sources, such as supernova remnant shocks and eventually propagate in the Galactic volume, occasionally interacting with gas, mainly in the disc of the Galaxy, and there they produce secondary nuclei through spallation. At sufficiently high energy, typically $\gtrsim 100$ GeV/n, the ratio of fluxes of the secondary nucleus to that of the main primary nucleus is found to scale as $E_{k}^{-δ}$, where $E_{k}$ is the energy per nucleon (a conserved quantity in spallation reactions) and $δ$ identifies the energy dependence of the diffusion coefficient. The same shock waves that may be responsible for cosmic ray acceleration in the first place also pick up any other charged particle in the upstream, provided being above threshold for injection. The secondary nuclei produced by spallation in the interstellar medium are no exception, hence they also get accelerated. This effect is unavoidable, only its strength may be subject of debate. We compute the spectrum of secondary elements such as boron and lithium taking into account shock reacceleration and compare our predictions with the recent observations of the B/C ratio and preliminary measurements of the boron and lithium flux. Both these sets of data seem to confirm that reacceleration of secondary nuclei indeed plays an important role, thereby affecting the validity of those scaling rules that are often used in cosmic ray physics.

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