Cosmic-ray ionisation in circumstellar discs
Cosmic-ray ionisation in circumstellar discs
复制标题
星周盘中的宇宙射线电离
DOI：
10.1051/0004-6361/201732202
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发表时间：
2018
影响因子：
6.5
通讯作者：
H Germany
中科院分区：
文献类型：
--
作者：
M. Padovani;A. Ivlev;D. Galli;Paola Caselli INAF;Italy.;M. P. I. Garching;H Germany
上下文。银河系宇宙射线(CRS)是星际气体普遍存在的电离来源，在确定分子云和星周圆盘中电子、离子和带电尘埃颗粒的分数丰度方面与紫外线和X射线光子以及自然放射性竞争。
目标。我们模拟了银河系CRS各种成分的传播与气体的柱密度之间的关系。我们的研究集中在高密度下的传播，在几克厘米−2以上，特别是与崩塌的云和星盘的内部区域有关。
方法：研究方法。一次和二次CR粒子(质子和较重的原子核、电子、正电子和光子)的传播是在连续减速近似、扩散近似或灾变近似下通过对各种输运机制采用匹配过程来计算的。选择合适的机制取决于被建模为连续或灾难性的主导损失过程的性质。
结果。CR电离率是由≈130g cm−2以下的CR质子及其次级电子和≈600g cm−2以上的光子衰变产生的电子-正电子对决定的。我们指出，对于后一种情况，粒子输运的正确描述是计算电离率所必需的，因为电子和正电子的微分通量敏感地依赖于质子和光子的通量。
结论。我们的结果表明，在高密度环境中，如坍塌分子云的内部或星盘的中面，CR电离率比先前假设的要高。它不是随着柱密度的增加而指数下降，而是遵循更复杂的行为，因为支配次级粒子产生和传播的不同过程的相互作用。
Context. Galactic cosmic rays (CRs) are a ubiquitous source of ionisation of the interstellar gas, competing with UV and X-ray photons as well as natural radioactivity in determining the fractional abundance of electrons, ions, and charged dust grains in molecular clouds and circumstellar discs.
Aims. We model the propagation of various components of Galactic CRs versus the column density of the gas. Our study is focussed on the propagation at high densities, above a few g cm−2, especially relevant for the inner regions of collapsing clouds and circumstellar discs.
Methods. The propagation of primary and secondary CR particles (protons and heavier nuclei, electrons, positrons, and photons) is computed in the continuous slowing down approximation, diffusion approximation, or catastrophic approximation by adopting a matching procedure for the various transport regimes. A choice of the proper regime depends on the nature of the dominant loss process modelled as continuous or catastrophic.
Results. The CR ionisation rate is determined by CR protons and their secondary electrons below ≈130 g cm−2 and by electron-positron pairs created by photon decay above ≈600 g cm−2. We show that a proper description of the particle transport is essential to compute the ionisation rate in the latter case, since the electron and positron differential fluxes depend sensitively on the fluxes of both protons and photons.
Conclusions. Our results show that the CR ionisation rate in high-density environments, such as the inner parts of collapsing molecular clouds or the mid-plane of circumstellar discs, is higher than previously assumed. It does not decline exponentially with increasing column density, but follows a more complex behaviour because of the interplay of the different processes governing the generation and propagation of secondary particles.
影响因子：
8.6
作者：
M. Aguilar;D. Aisa;A. Alvino;G. Ambrosi;K. Andeen;L. Arruda;N. Attig;P. Azzarello;A. Bachlechner-A.
通讯作者：
M. Aguilar;D. Aisa;A. Alvino;G. Ambrosi;K. Andeen;L. Arruda;N. Attig;P. Azzarello;A. Bachlechner-A.
宇宙射线强子的π介子产生动量损失
DOI：
10.1088/0004-637x/802/2/114
发表时间：
2015
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Krakau;Schlickeiser
通讯作者：
Schlickeiser