AI 中文总结
该研究利用宇宙线偶极各向异性的方向与强度，结合三维传播模拟，约束了“脚踝”以下中等质量核的起源，证实其河外起源符合观测，而银河系源无法解释相关各向异性特征。
AI 中文摘要
能量高于8EeV的宇宙线（CR）通量空间分布呈现出显著的偶极各向异性，这与河外宇宙线源遵循大尺度结构的预期相符；在“脚踝”处，方向突然改变，与能量≤4EeV时的银河系中心方向一致。我们利用偶极各向异性的方向和强度作为诊断工具，研究“脚踝”以下中等质量核的可能起源，这类核无法与低能银河系CR的彼得斯循环延续性关联。通过在最新银河系磁场模型中进行CR传播的三维模拟，我们发现，连续及瞬时的单个银河系源、源分布产生的偶极各向异性均超出观测测量值达3σ以上；而“脚踝”以下中等质量核的河外起源则与所有数据吻合，观测到的偶极方向变化由在“第二膝”处占主导的重银河系成分衰减所引导。
英文摘要
The spatial distribution of the cosmic-ray (CR) flux above $8\,\mathrm{EeV}$ exhibits a significant dipole in agreement with expectations from extragalactic sources following the large-scale structure. At the ankle, the direction changes suddenly and is compatible with the Galactic center for energies $\lesssim4\,\mathrm{EeV}$. We leverage the direction and strength of the dipole anisotropy as diagnostics of the possible sources of the intermediate-mass nuclei below the ankle that cannot be associated with the continuation of the Peters cycle of lower-energy Galactic CRs. Using 3D-simulations of CR propagation in up-to-date Galactic magnetic field models, we show that the dipole anisotropy of both continuous and transient individual Galactic sources and source distributions exceeds the measurements by $>3σ$. An extragalactic origin of the intermediate nuclei below the ankle instead agrees with all data, where the observed change in dipole direction is guided by the fading heavy Galactic component dominant at the second knee.
