标题： 使用EUHFORIA研究行星际日冕物质抛射的径向演化 显示英文标题

标题： Exploring the radial evolution of Interplanetary Coronal Mass Ejections using EUHFORIA

摘要： 日冕物质抛射（CMEs）是从太阳向星际空间的大规模喷发。 尽管CME是主要的空间天气驱动因素，但由于在1 au以外的距离观测数据稀缺，我们对内日球层中CME特性的了解仍然有限。 此外，大多数CME都是由单个航天器就地观测的，需要数值模型来补充现有的稀疏观测数据。 我们的目标是评估EUHFORIA中线性力自由球形环状CME模型描述行星际CME径向演化的能力，为观测研究提供新的背景。 我们模拟了一个广泛研究的CME，并通过在模拟区域内的日地线上放置虚拟航天器来研究其径向演化。 为了直接比较观测结果和模拟结果，我们从模型生成的时间序列中表征了0.2到1.9 au之间的行星际CME特征，利用传统上用于分析真实就地数据的技术。 结果表明，模型中平均太阳风和CME值的径向演化与观测和理论预期一致。 由于周围风中的压力衰减，CME发生膨胀：在0.4 au以内膨胀迅速，而在更远的距离上膨胀较缓。 早期的快速膨胀无法解释模拟中高估的CME径向尺寸，这表明这是所用球形环状几何结构的固有局限性。 磁场分布表明CME在传播过程中发生了松弛，而年龄效应可能不是0.4 au以外磁不对称性的主要来源。 我们还报告了一个比观测结果建议的要短得多的CME尾流。 总体而言，EUHFORIA提供了对太阳风和CME径向演化的连贯描述；然而，仍需改进以更好地再现CME的径向扩展。 显示英文摘要

摘要： Coronal Mass Ejections (CMEs) are large-scale eruptions from the Sun into interplanetary space. Despite being major space weather drivers, our knowledge of the CME properties in the inner heliosphere remains constrained by the scarcity of observations at distances other than 1 au. Furthermore, most CMEs are observed in situ by single spacecraft, requiring numerical models to complement the sparse observations available. We aim to assess the ability of the linear force-free spheromak CME model in EUHFORIA to describe the radial evolution of interplanetary CMEs, yielding new context for observational studies. We model one well-studied CME, and investigate its radial evolution by placing virtual spacecraft along the Sun-Earth line in the simulation domain. To directly compare observational and modelling results, we characterise the interplanetary CME signatures between 0.2 and 1.9 au from modelled time series, exploiting techniques traditionally employed to analyse real in situ data. Results show that the modelled radial evolution of the mean solar wind and CME values is consistent with observational and theoretical expectations. The CME expands as a consequence of the decaying pressure in the surrounding wind: the expansion is rapid within 0.4 au, and moderate at larger distances. The early rapid expansion could not explain the overestimated CME radial size in our simulation, suggesting this is an intrinsic limitation of the spheromak geometry used. The magnetic field profile indicates a relaxation of the CME during propagation, while ageing is most probably not a substantial source of magnetic asymmetry beyond 0.4 au. We also report a CME wake that is significantly shorter than suggested by observations. Overall, EUHFORIA provides a consistent description of the radial evolution of solar wind and CMEs; nevertheless, improvements are required to better reproduce the CME radial extension.