近日，老挝黄金赌场高能物理研究所的陈松战及其研究小组与香港中文大学的吳震宇等人合作并取得一项新进展。经过不懈努力，他们在日冕磁场存在的情况下模拟宇宙射线与太阳大气相互作用产生的伽马射线。相关研究成果已于2024年4月15日在国际知名学术期刊《中国物理C》上发表。

在本研究中，研究人员运用势场源面（PFSS）模型，在日冕磁场环境下模拟了太阳大气中粒子的相互作用，以解开低能伽马射线产生机制这一谜团。他们发现，在日冕磁场的影响下，低能（约GeV）伽马射线的产生得到了显著增强，但这种增强效果随着能量的增加而迅速减弱。这一增强现象与产生伽马射线时存在的较大偏差角，相对于输入宇宙射线方向，有着直接的关联。

因此，研究人员得出结论，在模拟低于10 GeV的太阳盘伽马射线时，日冕磁场的作用至关重要。然而，对于高于10 GeV的伽马射线，日冕磁场的影响逐渐减弱，需要探索其他磁场结构来解释高能圆盘发射现象。

据悉，宇宙射线在与太阳大气相互作用时，会激发出大量的次级信使，使得太阳成为夜空中一个璀璨的伽马射线源。Fermi-LAT的细致观测显示，这些相互作用过程深受太阳磁场的强烈影响，进而产生诸如高通量和硬光谱等广泛的观测特征。然而，这些特征背后的具体作用机制至今仍是一个未解之谜。

附：英文原文

Title: Simulating gamma-ray production from cosmic rays interacting with the solar atmosphere in the presence of coronal magnetic fields

Author: Zhe Li, Kenny C. Y. Ng, Songzhan Chen, Yuncheng Nan, Huihai He

Issue&Volume: 2024-04-15

Abstract: Cosmic rays can interact with the solar atmosphere and produce a slew of secondary messengers, making the Sun a bright gamma-ray source in the sky. Detailed observations with Fermi-LAT have shown that these interactions must be strongly affected by solar magnetic fields in order to produce a wide range of observational features, such as a high flux and hard spectrum. However, the detailed mechanisms behind these features are still a mystery. In this study, we tackle this problem by performing particle-interaction simulations in the solar atmosphere in the presence of coronal magnetic fields using the potential field source surface (PFSS) model. We find that low-energy (~ GeV) gamma-ray production is significantly enhanced by the coronal magnetic fields, but the enhancement decreases rapidly with energy. The enhancement directly correlates with the production of gamma rays with large deviation angles relative to the input cosmic-ray direction. We conclude that coronal magnetic fields are essential for correctly modeling solar disk gamma rays below 10 GeV, but above that, the effect of coronal magnetic fields diminishes. Other magnetic field structures are needed to explain the high-energy disk emission.

DOI: 10.1088/1674-1137/ad1cda

Source: http://hepnp.ihep.ac.cn/article/doi/10.1088/1674-1137/ad1cda