Evolution of Coronal Mass Ejections in the Inner Heliosphere: A Study Using White-Light and Scintillation Images
Evolution of Coronal Mass Ejections in the Inner Heliosphere: A Study Using White-Light and Scintillation Images
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DOI：
10.1007/s11207-006-0100-y
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发表时间：
2006-05
期刊：
影响因子：
2.8
通讯作者：
P. Manoharan
中科院分区：
文献类型：
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作者：
P. Manoharan
了解日冕物质抛射(CME)的径向演化对于理解其到达近地空间以及在其行进到1AU甚至更远的过程中与扰动/环境太阳风的相互作用具有重要意义。本文利用(I)SOHO任务上的大角度光谱日冕仪(LASCO)的近太阳区域白光图像和(Ii)Ooty射电望远镜获得的内日光层的行星际闪烁图像，研究了30个大型日冕物质抛射(角宽度和150∘，即晕和部分晕CME)的径向演化。在LASCO的日心距视场R≤30太阳半径(R⊙)内，这些日冕物质抛射覆盖了一个数量级的初始速度范围，VCME≈260-2600 KM S−1。从这些日冕物质抛射在日地距离范围内的速度演化得到以下结果：(1)CME的速度廓线与其初始速度有关；(2)CME的传播经历了连续的变化，这取决于CME与途中遇到的周围太阳风的相互作用；(3)综合LASCO和IPS图像得到的径向速度廓线反映了日冕物质抛射在内日球层中传播的实际情况，由这些廓线计算出的日冕物质抛射在1AU处的传播时间和速度与实际测量结果吻合较好：(4)不同初始速度的平均走时曲线和径向速度廓线的形状表明，在∼80r⊙范围内，CME的内部能量(或CME的扩展)占主导地位，但在较大距离上，CME与太阳风的相互作用控制了CME的传播；(5)大多数日冕物质抛射倾向于在1AU或更远距离地球轨道时达到环境气流的速度。这项研究的结果对于量化CME与周围太阳风的相互作用对CME施加的阻力是有用的，这对于模拟CME的传播是必不可少的。这项研究对理解CME相关的近地空间天气预报也具有重要意义。
Knowledge of the radial evolution of the coronal mass ejection (CME) is important for the understanding of its arrival at the near-Earth space and of its interaction with the disturbed/ambient solar wind in the course of its travel to 1 AU and further. In this paper, the radial evolution of 30 large CMEs (angular width > 150∘, i.e., halo and partial halo CMEs) has been investigated between the Sun and the Earth using (i) the white-light images of the near-Sun region from theLarge Angle Spectroscopic Coronagraph(LASCO) onboard SOHO mission and (ii) theinterplanetary scintillation(IPS) images of the inner heliosphere obtained from the Ooty Radio Telescope (ORT). In the LASCO field of view at heliocentric distancesR≤30 solar radii (R⊙), these CMEs cover an order of magnitude range of initial speeds,VCME≈260–2600 km s−1. Following results have been obtained from the speed evolution of these CMEs in the Sun–Earth distance range: (1) the speed profile of the CME shows dependence on its initial speed; (2) the propagation of the CME goes through continuous changes, which depend on the interaction of the CME with the surrounding solar wind encountered on the way; (3) the radial-speed profiles obtained by combining the LASCO and IPS images yield the factual view of the propagation of CMEs in the inner heliosphere and transit times and speeds at 1 AU computed from these profiles are in good agreement with the actual measurements; (4) the mean travel time curve for different initial speeds and the shape of the radial-speed profiles suggest that up to a distance of ∼80R⊙, the internal energy of the CME (or the expansion of the CME) dominates and however, at larger distances, the CME's interaction with the solar wind controls the propagation; (5) most of the CMEs tend to attain the speed of the ambient flow at 1 AU or further out of the Earth's orbit. The results of this study are useful to quantify the drag force imposed on a CME by the interaction with the ambient solar wind and it is essential in modeling the CME propagation. This study also has a great importance in understanding the prediction of CME-associated space weather at the near-Earth environment.