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arXiv 0909.0534astro-ph.SR
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从日球层的伸长测量导出宽日冕物质抛射的径向距离--对CME-CME相互作用的应用

Deriving the radial distances of wide coronal mass ejections from elongation measurements in the heliosphere - Application to CME-CME interaction

N. Lugaz, A. Vourlidas, I. I. Roussev

摘要:

我们提出了一般的考虑有关推导的径向距离的日冕物质抛射(CME)的伸长角测量,如SECCHI和SMEI提供的,侧重于测量的日光层成像仪2(HI-2)的视野(即过去0.3 AU)。这项研究是基于一个三维(3-D)磁流体动力学(MHD)模拟的两个CME观测SECCHI在2007年1月24日至27日。具有合成HI图像的3-D模拟,我们能够比较用于从伸长角导出CME位置的两种基本方法,即所谓的“P点”和“固定Φ”近似。我们确认,类似的工作,这两种方法,而有效的最内层日光层,产生越来越大的错误HI-2的视野快速和广泛的日冕物质抛射。使用一个简单的模型的日冕物质抛射作为一个不断扩大的自相似球,我们推导出一个解析关系的伸长角和径向距离宽日冕物质抛射。这种关系只是“P点”和“固定Φ”近似的调和平均值,其目的是通过锥模型或磁绳形状补充CME的3-D拟合。当我们将视线的结果与MHD模拟的结果进行比较时,它证明了更好地获得模拟CME的运动学。基于这种近似,我们重新分析了2007年1月26日至27日的J图(时间延长图),并提出了第一个观测证据,CME的合并是与动量交换从快速喷射到较慢的一个由于传播的冲击波与快速喷发通过缓慢喷发。

英文摘要:

We present general considerations regarding the derivation of the radial distances of coronal mass ejections (CMEs) from elongation angle measurements such as those provided by SECCHI and SMEI, focusing on measurements in the Heliospheric Imager 2 (HI-2) field of view (i.e. past 0.3 AU). This study is based on a three-dimensional (3-D) magneto-hydrodynamics (MHD) simulation of two CMEs observed by SECCHI on January 24-27, 2007. Having a 3-D simulation with synthetic HI images, we are able to compare the two basic methods used to derive CME positions from elongation angles, the so-called "Point-P" and "Fixed-Phi" approximations. We confirm, following similar works, that both methods, while valid in the most inner heliosphere, yield increasingly large errors in HI-2 field of view for fast and wide CMEs. Using a simple model of a CME as an expanding self-similar sphere, we derive an analytical relationship between elongation angles and radial distances for wide CMEs. This relationship is simply the harmonic mean of the "Point-P" and "Fixed-Phi'' approximations and it is aimed at complementing 3-D fitting of CMEs by cone models or flux rope shapes. It proves better at getting the kinematics of the simulated CME right when we compare the results of our line-of-sights to the MHD simulation. Based on this approximation, we re-analyze the J-maps (time-elongation maps) in January 26-27, 2007 and present the first observational evidence that the merging of CMEs is associated with a momentum exchange from the faster ejection to the slower one due to the propagation of the shock wave associated with the fast eruption through the slow eruption.

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