Possible effects of geomagnetic polarity transitions on the biosphere

地球拥有至少35亿年的全球磁场。这个地磁场表现出重大的时间变化，其中最戏剧性的一次是极性转变。由于在这种转变过程中，表面场几乎塌陷，因此这种塌缩可能产生的影响是最重要的问题。如果高能粒子在极性转变期间更好地进入大气层，这可能会导致中间大气中的硝酸氧水平增加，从而导致臭氧层柱密度下降和表面UV-B辐射相应增加。为了更好地理解磁层-电离层-大气-生物圈耦合系统，我们建议开发详细的模型，研究这种UV-B水平增加对选定的水生生态系统的影响。通过使用描述极性转换过程中大气硝态氧增加和伴随的UV-B增加的模型、生物光学和浮游植物模型以及进化模型，我们想要检验(I)生物圈对地磁场变化及其延迟时间的非线性响应，(Ii)不同物种的水生生态系统对极性转换引起的UV-B辐射变化的敏感性和可能的进化效应。拟议研究的另一个目的是确定能够证明磁层-电离层-大气层-生物圈系统关于极性转变的拟议反应序列的替代物。

The Earth possesses a global magnetic field for at least 3.5 billion years. This geomagnetic field exhibits major temporal variations with the most dramatic one being a polarity transition. As during such a transition the surface field almost collapses the question of possible effects of this collapse is a most important one. If energetic particles have much better access to the atmosphere during a polarity transition, this may cause an increased nitric oxygen level in the middle atmosphere with a resulting decrease of the ozone column density and a corresponding increase in the surface UV-B radiation. In order to better understand the coupled magnetosphere-ionosphere-atmosphere-biosphere system we propose to develop detailed models of the effect of such a UV-B level increase on selected aquatic ecosystems. By using models describing the atmospheric nitric oxygen increase and the associated UV-B increase during polarity transitions, a bio-optical and phytoplankton model as well as an evolutionary model we want to test (i) the nonlinear response of the biosphere on geomagnetic field changes and its delay times, (ii) the sensitivity of different species of the aquatic ecosystem to polarity transition induced UV-B radiation changes and possible evolutionary effects. Another aim of the proposed studies is the identification of proxies that show evidence for the proposed reaction sequence of the magnetosphere-ionosphere-atmospherebiosphere system on polarity transitions.