Wenyuan Yu, Nada Al-Haddad, Charles J. Farrugia, Noé Lugaz, Bin Zhuang, Florian Regnault and Antoinette B. Galvin
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引用次数: 0
摘要
本研究的目的是利用多航天器对行星际磁云(MC)的测量,更好地约束和理解膨胀对其磁场特性的影响。我们开发了一个参数(γ),用于比较多个航天器测量到的磁场成分。我们利用磁场数据的最小方差技术来获得轴向和方位角分量。参数γ作用于前边界,衡量 MC 的轴向和方位角磁场分量随日光层距离演变的总体差异。我们的目标是确定所研究的 MC 是否呈现自相似膨胀,如果是,则根据估算的 γ 值确定这种膨胀主要是各向同性的还是径向的。我们发现,这些 MCs 的整体膨胀趋于各向同性,而 MCs 的局部膨胀(根据 MCs 后边界测量的 γ 值推导)通常表现为各向异性,尤其是当两个航天器的观测距离相对较短时。这一发现为完善通量绳模型和推进我们对与日冕物质抛射相关的膨胀过程的理解提供了启示。
Measurements of Magnetic Cloud Expansion through Multiple Spacecraft in Radial Conjunction
The aim of this study is to use multispacecraft measurements of interplanetary magnetic clouds (MCs) to better constrain and understand the effect of expansion on their magnetic field properties. We develop a parameter (γ) for comparing magnetic field components measured at multiple spacecraft. We use the minimum variance technique on the magnetic field data to obtain the axial and azimuthal components. The parameter γ acts at the front boundary as a measure of the global difference in the evolution with heliospheric distance of the axial and azimuthal magnetic field components of MCs. Our goal is to determine whether the studied MCs exhibit self-similar expansion and, if so, whether this expansion is predominantly isotropic or radial, based on the estimated γ. Through our analysis of data from multiple spacecraft, we observe a notable consistency in the γ values across the examples examined. We find that the overall expansion of these MCs tends to be isotropic, while the local expansion of MCs, derived from the γ values measured at the rear boundary of MCs, usually shows anisotropic behavior, particularly when the distances between the observations from the two spacecraft are relatively short. This discovery offers insights for refining flux rope models and advancing our comprehension of the expansion processes associated with coronal mass ejections.