Cosmic Ray Anisotropy and Interstellar Spectra: Astrophysics of the Outer Heliosphere

地面和天基探测器的各种测量揭示了正确理解日球层物理学与天体物理学的相关性。最重要的是与日球层外边界有关的观测。首先，随着旅行者号航天器的不断改进，宇宙射线的局部星际光谱的测定得到了不断的改进。第二，旅行者号，特别是IBEX任务增加了我们对当地星际磁场、等离子体和日球层周围的中性气体的定量认识。两者都引发了对宇宙射线调制的精细理解。第三，观测到的宇宙射线在低tev范围内的各向异性部分是由日球层结构引起的假设，最近得到了一些陆地大面积粒子探测器和望远镜的测量结果的支持，以及关于日尾磁重联等理论考虑的支持。为了判断对外层日球层的正确物理描述及其天体物理相关性的各种建议，我们将开发考虑日球层及其星际附近大尺度结构的定量模型，特别是包括所谓的日鞘和日尾以及局部星际磁场。因此，本提案的主要目标定义如下：我们将通过自洽地包括磁场来扩展我们先前嵌入星际介质的大规模日球层模型-特别是关于高度细长的日球层尾巴-我们将通过求解这些粒子的输运方程和运动方程来研究相应的宇宙射线通量。因此，我们可以测试太阳尾是否确实影响宇宙射线通量在低tev范围内的各向异性。此外，该模型使我们能够研究外日球层结构对局部星际宇宙射线谱的影响。对于这些应用，我们将引入新的，所谓的逻辑矩形网格到日球层建模中，因为目前使用的网格有严重的缺点。这些新网格的优点是可以根据问题的几何形状进行局部调整，避免了坐标奇异性和不同的单元大小。该项目的结果将包括对我们的直接天体物理环境的建模，这将首次允许在天体物理观测中对潜在的日球层特征进行定量解释。

Various measurements with ground- and space-based detectors have revealed the astrophysical relevance of a correct understanding of heliospheric physics. Most important for the proposed project are those observations related to outer bundary of the heliosphere. First, the determination of the local interstellar spectra of cosmic rays is improved continuously with the Voyager spacecraft. Second, the Voyagers and, particularly, the IBEX mission have increased our quantitative knowledge about the local interstellar magnetic field, plasma, and neutral gas surrounding the heliosphere. Both have triggered a refined understanding of cosmic ray modulation.Third, the hypothesis that the observed cosmic ray anisotropy in the low-TeV range is partly caused by the heliospheric structure, has recently gained new support from measurements with several terrestrial large area particle detectors and telescopes, as well as from theoretical considerations regarding, for example, magnetic reconnection in the heliotail. In order to judge on the various suggestions for the correct physical description of the outer heliosphere and its astrophysical relevance, we will develop quantitative models accounting for the large-scale structure of the heliosphere and its interstellar vicinity, particularly including the so-called heliosheath and heliotail as well as the local interstellar magnetic field. Consequently, the main objectives of the present proposal are defined as follows: We will extend our previous modelling of the large-scale heliosphere embedded in the interstellar medium by self-consistently including magnetic fields - especially with respect to the highly elongated heliospheric tail - and we will study the corresponding cosmic ray flux by solving both the transport equation and the equation of motion for these particles. Thus, we can test whether the heliotail indeed affects the anisotropy of the cosmic ray flux in the low-TeV range. Furthermore, this model allows us to study the effect of outer heliospheric structures on the local interstellar cosmic ray spectra. For these applications we will introduce new, so-called logically rectangular grids into heliospheric modelling since the presently used ones have severe shortcomings. These new grids have the advantages of being locally adjustable to the problem's geometry, avoiding both coordinate singularities and strongly differing cell sizes. The project results will consist of a modelling of our direct astrophysical environment, that will allow, for the first time, a quantitative interpretation of potential heliospheric signatures in astrophysical observations.