AI 中文总结
本研究通过多航天器观测96个磁云，用Gold--Hoyle通量绳模型重构ICME内部磁场，发现轴向场强和扭缠密度随日心距离增大而减小，扭缠密度上限遵循特定尺度关系，为行星际磁通量绳演化提供观测约束。
AI 中文摘要
行星际日冕物质抛射（ICMEs）是引发日球层扰动与空间天气效应的主要驱动因素。本文开展了一项多航天器研究，研究对象为分布在大范围日心距离上的96个磁云（MCs），并采用均匀扭缠的Gold--Hoyle（GH）通量绳模型重构其内部磁场结构。通过拟合，我们推导得到轴向场强$B_0$、扭缠密度（匝数密度）$τ$、GH参数$ω$以及积分扭缠数$n$。研究发现，$B_0$与匝数密度$τ$均随日心距离增大而减小，这与传播过程中的膨胀和轴向拉伸效应一致。一项关键结果是，$τ$--$R$平面中的上包络对应于无量纲GH参数$ω=2πRτ$的近似恒定边界，其值接近$ω\thicksim2$。因此，推断得到的$τ$上限值并非与尺度无关，而是对于给定的通量绳半径遵循$τ_{\text{max}}\backsimeq ω_{\text{max}}/(2πR)$的关系。相比之下，在当前样本中，估算得到的积分匝数$n$未表现出类似清晰的径向分布规律。本研究探究了0.07至5.4 AU日心距离范围内的ICME结构与磁场特征，从而为行星际磁通量绳的大尺度演化提供了观测约束。
英文摘要
Interplanetary coronal mass ejections (ICMEs) are major drivers of heliospheric disturbances and space-weather effects. Here we present a multi-spacecraft study of 96 magnetic clouds (MCs) distributed over a broad range of heliocentric distances, and reconstruct their internal magnetic structure with a uniform-twist Gold--Hoyle (GH) flux-rope model. From the fits, we derive the axial field strength $B_0$, the twist density (turn density) $τ$, the GH parameter $ω$, and the integrated twist number $n$. We find that $B_0$ and the turn density $τ$ both decrease with increasing heliocentric distance, consistent with expansion and axial stretching during propagation. A key result is that the upper envelope in the $τ$--$R$ plane corresponds to a nearly constant boundary in the dimensionless GH parameter $ω=2πRτ$, close to $ω\sim2$. Therefore, the inferred upper value of $τ$ is not scale-independent, but follows $τ_{\max}\simeq ω_{\max}/(2πR)$ for a given flux-rope radius. In contrast, the estimated integrated turn number $n$ shows no similarly clear radial organization in the present sample. This study investigates the ICME structure and magnetic field characteristics across heliocentric distances from 0.07 to 5.4~AU, thereby providing observational constraints on the large-scale evolution of interplanetary magnetic flux ropes.
