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

使用地面和天基探测器进行的各种测量揭示了正确理解日球层物理的天体物理相关性。对拟议的项目来说，最重要的是与日光层外界有关的观测。首先，随着旅行者号航天器的不断完善，宇宙射线的局部星际光谱的测定不断得到改进。其次，旅行者号，特别是IBEX任务增加了我们对日光层周围的星际磁场、等离子体和中性气体的定量知识。两者都引发了对宇宙线调制的精细理解。第三，关于在低TeV范围内观测到的宇宙线各向异性部分是由日球层结构造成的假设，最近从几个地面大面积粒子探测器和望远镜的测量以及关于例如日尾磁重联的理论考虑中获得了新的支持。为了判断关于正确描述外部日光层及其天体物理相关性的各种建议，我们将开发考虑日光层及其星际附近的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，本提案的主要目标界定如下：我们将通过自洽地包括磁场--特别是关于高度拉长的日光层尾部--来扩展我们先前对嵌入星际介质中的大规模日光层的模拟，并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，我们可以测试在低TeV范围内日尾是否确实影响宇宙线通量的各向异性。此外，该模型还允许我们研究外部日球层结构对星际宇宙线局域光谱的影响。对于这些应用，我们将在日球层建模中引入新的所谓逻辑矩形网格，因为目前使用的网格存在严重缺陷。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明显不同的单元大小。该项目的成果将包括对我们的直接天体物理环境进行建模，这将首次使我们能够对天体物理观测中的潜在日光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.