利用甚高能宇宙线开展日地空间磁场相关物理研究

With the development of EAS arrays, the sensitivity of ground-based cosmic ray experiments (such as ASγ, ARGO-YBJ, HAWC and LHAASO) for Sun shadow is significantly improved. This provides an opportunity for the new method to probe solar-terrestrial space magnetic field using cosmic ray, which can make up for the insufficient of current measurement. In this project, we will develop a complete program to trace the cosmic ray within solar-terrestrial space. With this program, we can systematically study the influence of the coronal magnetic field, solar dipole magnetic field, interplanetary magnetic field and CME events on the Sun shadow. This is important for the new method to probe the magnetic field using cosmic ray. With this research, we can provide methods for current and future EAS arrays to carry out corresponding data and physics analysis. In this project, we will make a quantitative measurement for the solar dipole magnetic field and also test the current coronal magnetic field models through the energy dependent of Sun shadow using experimental data of ARGO-YBJ and LHAASO for the first time. With these measurements, we can further study the evolution of solar dipole magnetic field and coronal magnetic field during the solar activity period. This research will provide important observational evidence for the study of the related physics of solar magnetic field and solar-terrestrial background magnetic field. We will also study the capacity of future LHAASO experiment and their response to the CME event, then to study the feasibility of space weather forecast using cosmic ray experiment.

随着探测器规模扩大，地面宇宙线实验（中日ASγ、中意ARGO-YBJ、美国HAWC和中国LHAASO）对宇宙线日影的灵敏度越来越高，这为以宇宙线为探针测量日地空间磁场这种新方法提供了锲机，可以弥补现有空间磁场测量手段的不足。本项目将建立一套完整的宇宙线在日地空间追踪程序，研究日冕磁场、太阳偶极场、行星际磁场及CME事件对日影的影响规律和特征，完善利用宇宙线开展日地空间磁场测量这一新方法，为各家宇宙线实验开展相关数据和物理分析提供方法依据；并利用ARGO-YBJ和未来的LHAASO实验数据首次对太阳偶极场进行定量测量、首次测量日影缺失率的能谱依赖关系并以此检验现有日冕磁场模型，并进一步研究太阳偶极场和日冕磁场随太阳活动的演化，为太阳磁场和日地空间背景磁场相关物理研究提供重要的观测依据；还将研究未来LHAASO实验对CME事件的响应情况，研究利用宇宙线实验开展空间天气预报的可行性。

宇宙线为带正电粒子，在达到地球前受太阳系和地球磁场影响，基于宇宙线相关观测（如日影和大尺度各向异性等）可以研究日地空间相关磁场。本项目建立了一套完整的宇宙线在日地空间追踪程序，研究并得到了日冕磁场、行星际磁场及地磁场对日影的影响规律和特征，为利用宇宙线开展日地空间磁场测量提供方法依据；另外还建立太阳伽马射线辐射模拟程序，在国际上首次给出了太阳磁场对伽马辐射影响的定量估计。基于位于羊八井的中意合作ARGO-YBJ实验数据开展了对宇宙线日影研究，在国际上首次得到了太阳活动与日影特征能量定量关系；开展了宇宙线大尺度各向异性稳定性研究，结果显示宇宙线各向异性在TeV以上不随太阳磁场活动变化，否定了美国Milagro实验结论；开展太阳伽马射线辐射研究，给出了太阳平静期伽马射线流强上限。本项目还建立LHAASO-KM2A阵列模拟程序，并对LHAASO-KM2A的触发逻辑进行了优化，显著提高了其日影的观测灵敏度。