标题： 宇宙射线对撞击后早期地球大气的电离：在生命起源情景中必须考虑太阳宇宙射线的电离 显示英文标题

标题： Cosmic ray ionisation of a post-impact early Earth atmosphere: Solar cosmic ray ionisation must be considered in origin-of-life scenarios

摘要： 宇宙射线（CR），包括太阳和银河系的，会对地球的大气层产生电离作用，并被认为对原始分子的生成很重要。特别是，在蒸发海洋的撞击后形成的以$\rm{H_2}$为主的大气层被认为有利于原始分子的形成。我们模拟了太阳和银河系CR通过200Myr时的撞击后早期地球大气的传输。我们的目标是确定产生的电离率$\zeta$的差异，特别是在太阳非常活跃时期的地球表面。我们使用蒙特卡洛模型来描述CR通过早期地球大气的传输，给出CR能谱作为高度的函数。我们计算了$\zeta$和由于银河系和太阳CR在高度上的离子对产率$Q$。银河系和太阳CR能谱都受到太阳自转速率$\Omega$的影响，因为太阳风速度和磁场强度都取决于$\Omega$并影响CR传输。 我们考虑一系列输入光谱，这些光谱来源于可能的 $\Omega$范围，从 $3.5-15\, \Omega_{\rm{\odot}}$。 为了考虑太阳系外银河宇宙射线光谱在十亿年时间尺度上变化的可能性，我们将来自两种不同情景的顶层大气 $\zeta$进行比较。 我们还考虑了行星磁场对宇宙射线光谱的抑制作用。 我们发现，在大多数情况下，由于宇宙射线导致的 $\zeta$和 $Q$在早期地球大气中主要由太阳宇宙射线主导。 相应的$\zeta$在早期地球表面的范围从$5 \times 10^{-21}\rm{s^{-1}}$对于$\Omega = 3.5\,\Omega_{\rm{\odot}}$到$1 \times 10^{-16}\rm{s^{-1}}$对于$\Omega = 15\,\Omega_{\rm{\odot}}$。 因此，如果年轻的太阳是一个快速旋转体，那么太阳宇宙射线在生命可能形成的时候很可能对地球表面的化学反应产生了显著影响。 显示英文摘要

摘要： Cosmic rays (CR), both solar and Galactic, have an ionising effect on the Earth's atmosphere and are thought to be important for prebiotic molecule production. In particular, the $\rm{H_2}$-dominated atmosphere following an ocean-vaporising impact is considered favourable to prebiotic molecule formation. We model solar and Galactic CR transport through a post-impact early Earth atmosphere at 200Myr. We aim to identify the differences in the resulting ionisation rates, $\zeta$, particularly at the Earth's surface during a period when the Sun was very active. We use a Monte Carlo model to describe CR transport through the early Earth atmosphere, giving the CR spectra as a function of altitude. We calculate $\zeta$ and the ion-pair production rate, $Q$, as a function of altitude due to Galactic and solar CR. The Galactic and solar CR spectra are both affected by the Sun's rotation rate, $\Omega$, because the solar wind velocity and magnetic field strength both depend on $\Omega$ and influence CR transport. We consider a range of input spectra resulting from the range of possible $\Omega$, from $3.5-15\, \Omega_{\rm{\odot}}$. To account for the possibility that the Galactic CR spectrum outside the Solar System varies over Gyr timescales, we compare top-of-atmosphere $\zeta$ resulting from two different scenarios. We also consider the suppression of the CR spectra by a planetary magnetic field. We find that $\zeta$ and $Q$ due to CR are dominated by solar CR in the early Earth atmosphere for most cases. The corresponding $\zeta$ at the early Earth's surface ranges from $5 \times 10^{-21}\rm{s^{-1}}$ for $\Omega = 3.5\,\Omega_{\rm{\odot}}$ to $1 \times 10^{-16}\rm{s^{-1}}$ for $\Omega = 15\,\Omega_{\rm{\odot}}$. Thus if the young Sun was a fast rotator, it is likely that solar CR had a significant effect on the chemistry at the Earth's surface at the time when life is likely to have formed.