Astrospheric shielding of habitable planets

位于宜居带的系外行星的大气层顶部会受到银河系喜剧流和中性氢原子流的撞击。这些通量可以改变大气的组成，因此也可能改变生物特征，如臭氧或甲烷。银河宇宙线的通量以及来自星际介质的中性氢原子的通量强烈地受到天体层的影响。天体层是一个区域，在这个区域中，超快磁声恒星风膨胀，最后在星际介质的边界处产生激波结构。 由于恒星风和星际介质都有磁场，因此需要对天体层进行3D模拟。由于扩散张量依赖于所有三个空间维度，因此漫画射线的调制也需要用3D模拟来建模。在这个项目中，应建模天体层的3D结构。天体层的对称性取决于星际磁场的方向，星际磁场的方向将以45度的步长变化，以确定星际磁场方向的影响。此外，不同的恒星，其中有系外行星在可居住区，具有不同的风和星际环境将被建模。从这个模型中，中性氢的通量可以直接在行星的位置确定，而宇宙射线通量将由E。该项目的目标是确定行星际大气顶部的宇宙射线和中性氢通量，并找到一个简单的公式来描述这些通量。

The top of the atmosphere of an exo-planet in a habitable zone is hit by a galactic comic flux as well as a flux of neutral hydrogenatoms. These fluxes can change the composition of the atmosphere and therefore also possible bio signatures, like ozone or methane. The flux of the galactic cosmic rays as well as that of the neutral hydrogen atoms from the interstellar medium is strongly influenced by an astrosphere. The astrosphere is the region, in which the super fast-magnetsonic stellar wind expands and finally at the boundary to the interstellar medium a shock structure is created. Because the stellar wind as well as the interstellar medium have a magnetic field, a 3D simulation of the astrosphere is required. Also the modulation of the comic rays needs to be modeled with a 3D simulation, because the diffusion tensor depends on all three space dimensions.In this project the 3D structure of the astrosphere shall be modeled. The symmetry of the astrosphere depends on the orientation ofthe interstellar magnetic field, which will be varied in 45 degree steps to determine the influence of the orientation of the interstellar magnetic field. In addition different stars, which have exo-planets in the habitable zone, with different winds and interstellar environments will be modeled. From that models the flux of the neutral hydrogen can be determined directly at the position of the planet, while the cosmic ray flux will modeled with a 3D transport code by E. Engelbrecht using the 3D astrosphere models.The goal of the project is to determine the cosmic ray and neutral hydrogen flux at the top of an exo-planetary atmosphere and to find asimple formula to describe these fluxes.