再论地球磁场变化的生物学影响
Revisiting the Biological Ramifications of Variations in Earth's Magnetic Field
摘要：
一个类似地球的行星磁场已被广泛援引为可居住性的一个要求，因为它据称可以减轻到达表面的电离辐射通量以及中性粒子和离子从大气中逃逸。最近的古地磁证据表明，地球的内核的成核，随后可能是地磁场强度的增加，可能发生在埃迪卡拉纪附近。受这一假定发现的启发，我们探索了地球发电机的增长或逆转所产生的后果。通过审查和综合新出现的定量模型，提出在这些情况下，生物辐射剂量率和大气逃逸率的变化都不会超过$\sim 2$的系数。因此，我们认为，试图通过地球磁场强度的变化来解释寒武纪辐射或质量波动的假说可能是不可能的。我们还简要地讨论了行星磁场的变化可能会影响早期火星，并可能影响系外行星轨道M-矮星。
英文摘要：
An Earth-like planetary magnetic field has been widely invoked as a requirement for habitability as it purportedly mitigates the fluxes of ionizing radiation reaching the surface and the escape of neutrals and ions from the atmosphere. Recent paleomagnetic evidence indicates that the nucleation of Earth's inner core, followed perhaps by an increase in geomagnetic field strength, might have occurred close to the Ediacaran period. Motivated by this putative discovery, we explore the ensuing ramifications from the growth or reversals of Earth's dynamo. By reviewing and synthesizing emerging quantitative models, it is proposed that neither the biological radiation dose rates nor the atmospheric escape rates would vary by more than a factor of $\sim 2$ under these circumstances. Hence, we suggest that hypotheses seeking to explain the Cambrian radiation or mass extinctions via changes in Earth's magnetic field intensity are potentially unlikely. We also briefly discuss how variations in the planetary magnetic field may have impacted early Mars and could influence exoplanets orbiting M-dwarfs.
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