In situ measurements of coronal mass ejections (CMEs) when they pass over an interplanetary probe are one of the main ways we directly measure their properties. However, such in situ profiles are subject to several observational constraints that are still poorly understood. This work aims at quantifying one of them, namely, the aging effect, using a CME simulated with a three-dimensional magnetohydrodynamical code. The synthetic in situ profile and the instantaneous profile of the magnetic field strength differ more from each other when taken close to the Sun than far from it. Moreover, out of three properties we compute in this study (i.e., size, distortion parameter, and expansion speed), only the expansion speed shows a dependence of the aging as a function of distance. It is also the property that is the most impacted by the aging effect as it can amount to more than 100 km s⁻¹ for CMEs observed closer than 0.15 au. This work calls for caution when deducing the expansion speed from CME profiles when they still are that close to the Sun since the aging effect can significantly impact the derived properties.

中文翻译：

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探索老化效应对日冕物质抛射推断特性的影响

当日冕物质抛射（CME）经过行星际探测器时进行原位测量是我们直接测量其特性的主要方法之一。然而，这种原位剖面受到一些仍知之甚少的观测限制。这项工作旨在利用三维磁流体动力学代码模拟的 CME 来量化其中之一，即老化效应。当靠近太阳时，合成的原位磁场强度剖面和瞬时磁场强度剖面之间的差异比远离太阳时更大。此外，在本研究中我们计算的三个属性（即尺寸、畸变参数和膨胀速度）中，只有膨胀速度显示出老化与距离的函数关系。它也是受老化效应影响最大的属性，因为对于在接近 0.15 天文单位处观察到的日冕物质抛射，它可能达到超过 100 km s ^-1 。这项工作要求在从日冕物质抛射剖面推断膨胀速度时要小心，当它们仍然接近太阳时，因为老化效应会显着影响导出的特性。