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

几十年来，众所周知，太阳和月球都在几何上阻挡着地球上的宇宙射线，因此在空间分辨的宇宙线观测中产生了强度降低的区域，称为这些天体的“宇宙射线阴影”。能量在1TeV以上的带电宇宙射线还会在太阳日冕磁场中发生偏转。宇宙射线离子，主要是质子，通过它们与太阳大气物质的相互作用发起粒子簇射。在这些级联中，最终的衰变产物是伽马射线和中微子，它们分别可以被费米和冰立方等仪器探测到。此外，宇宙射线电子通过太阳辐射场上的逆康普顿散射产生额外的伽马射线。所有这些过程对太阳磁场都是直接或间接敏感的，因此，必须期望在这样的测量中留下印记。除了对太阳宇宙射线阴影、太阳伽马射线和中微子通量的磁场准确建模的重要性进行量化之外，这项研究还将允许在尚未在现场探索的地区推导出磁场本身的限制条件。该项目的中心目标是在高能宇宙线、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。只有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的研究领域)的知识，该项目才能成功实施。这项研究非常及时，因为它将结合这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、时变的磁场配置来提供宇宙射线粒子轨迹。其次，它将显著改进由于宇宙射线引发的级联而导致的伽马射线和中微子通量的计算。这两个研究小组在波鸿鲁尔大学已经开展的合作提供了一个独特的机会，可以对宇宙线传输及其相互作用和辐射过程作出统一的描述，这将为详细研究如何利用太阳磁场的特征提供机会，以便更好地了解磁场本身以及高能宇宙射线通过该磁场和日光层最深处的传输情况。

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.