Modeling the Time-Dependent Cosmic-Ray Sun Shadowand its related Gamma-Ray and Neutrino Signatures

几十年来，太阳和月球都被认为在几何上阻挡了地球的宇宙射线，从而在空间分辨的宇宙射线观测中产生了被称为这些天体的“宇宙射线阴影”的强度降低的区域。能量达到甚至超过1 TeV的带电宇宙射线在太阳日冕磁场中也会发生偏转。宇宙线离子，主要是质子，通过与太阳大气物质的相互作用引发粒子簇射。在这些级联的最终衰变产物中，有伽马射线和中微子，它们可以分别被费米和冰立方这样的仪器探测到。此外，宇宙射线电子通过太阳辐射场的逆康普顿散射产生额外的伽马射线。 所有这些过程都直接或间接地对太阳磁场敏感，因此，必须在此类测量中留下印记。除了量化太阳宇宙射线阴影，太阳伽马射线以及中微子通量的磁场精确建模的重要性外，该研究还将允许在尚未原位探索的区域中推导出磁场本身的约束。该项目的中心目标是在高能宇宙射线、伽马射线和中微子的测量中定量探索太阳磁场的特征，并解决目前存在的理论和测量之间的差异。该项目只能通过应用高能天体粒子物理学（J. Tjus的研究领域）和太阳物理学（H. Fichtner）。这项研究是非常及时的，因为它将通过结合两个研究领域的专业知识，对当代研究做出双重贡献。首先，它将以现实的、基于数据的、随时间变化的磁场配置提供宇宙射线粒子轨迹。第二，它将大大提高由于宇宙射线引发的级联的伽马射线和中微子通量的计算。鲁尔波鸿大学的两个研究小组之间已经存在的合作提供了一个独特的机会，可以对宇宙射线传输及其相互作用和辐射过程进行统一描述，这将为详细研究如何使用太阳磁场的特征打开大门，以便更好地了解磁场本身以及高能量的传输。能量宇宙射线穿过它和最里面的日光层。

For several decades, both the Sun and the Moon have been known to geometrically block Earth-bound cosmic rays, thus creating areas of reduced intensity in spatially resolved cosmic ray observations known as the "cosmic-ray shadow" of these celestial bodies. Charged cosmic rays up to and even above an energy of 1 TeV additionally experience a deflection in the solar coronal magnetic field. Cosmic ray ions, predominantly protons, initiate particle showers via their interaction with the solar atmospheric matter. Among the final decay products in these cascades are gamma-rays and neutrinos that can be detected by instruments like Fermi and IceCube, respectively. Furthermore, cosmic-ray electrons generate, via inverse-Compton scattering on the solar radiation field, additional gamma-rays. All these processes are directly or indirectly sensitive to the solar magnetic field that, therefore, must be expected to leave an imprint in such measurements. Besides quantifying the significance of an accurate modeling of the magnetic field for the Sun's cosmic-ray shadow, the solar gamma-ray as well as neutrino fluxes, the study will allow to derive constraints for the field itself in regions that are, as yet, not explored in situ. The central goal of the project is to quantitatively explore the signatures of the solar magnetic field in the measurements of high-energy cosmic rays, gamma-rays, and neutrinos, and to resolve the presently existing discrepancies between theory and measurements. The project can only be performed successfully by applying knowledge from both high-energy astroparticle physics (research area of J. Tjus) and heliophysics (research area of H. Fichtner). The study is very timely because it will, by combining expertise from the two research fields, contribute in a two-fold way to the contemporary research. First, it will deliver cosmic-ray particle trajectories in realistic, data-based, time-varying magnetic field configurations. Second, it will significantly improve the computation of gamma-ray and neutrino fluxes due to cosmic ray-initiated cascades. The already existing collaboration between the two research groups at the Ruhr-Universität Bochum offers a unique opportunity to develop a unified description of cosmic-ray transport and its interaction and radiation processes that will open the door for a detailed investigation of how signatures of the solar magnetic field can be used in order to better understand both the field itself as well as the transport of high-energy cosmic rays through it and the innermost heliosphere.