Multiple magnetic clouds: Several examples during March-April 2001
Multiple magnetic clouds: Several examples during March-April 2001
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DOI：
10.1029/2003ja009850
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发表时间：
2003-10
影响因子：
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通讯作者：
Yuming Wang;P. Ye;Shui Wang
中科院分区：
文献类型：
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作者：
Yuming Wang;P. Ye;Shui Wang
[1]多重磁云（Multi-MC）是行星际空间的一种复杂结构，是由连续的日冕物质抛射（CME）超越而形成的。多MC由于其特殊的性质和潜在的地缘效应而值得关注。利用ACE航天器的数据，我们确定在2001年3月至4月期间的三个多MC的情况下。结果表明，Multi-MC的观测特征是：（1）Multi-MC仅由多个磁云及其相互作用区组成，（2）Multi-MC中的每个子云基本上满足孤立磁云的标准，只是由于子云之间的压缩，质子温度不如典型磁云低;（3）太阳风在前云后部的速度不是持续减小，而是由于后云的超越而增大;（4）在次云相互作用区内部，磁场变得不规则，强度明显减弱，（5）在相互作用区，B值增大到一个较高的水平。我们发现三个多MC中有两个与大磁暴（Dst = 200 nT）有关，这表明多MC与某些强磁暴有着密切的联系。观测结果表明，多MC可能是大磁暴的另一种行星际起源，但并非所有的大磁暴都具有地球效应。根据太阳和日光层观测站（SOHO）和GOES的观测资料，对这些多MC的太阳源进行了识别。我们认为，这样的连续晕日冕物质抛射不需要起源于一个单一的太阳区域。此外，还分析了多MC与复杂喷出物的关系，并讨论了它们之间的一些异同。索引术语：2111行星际物理学：喷出物、驱动气体和磁云; 1739地球物理学史：太阳/行星关系; 7513太阳物理学、天体物理学和天文学：日冕物质抛射; 2788磁层物理学：风暴和亚暴;关键词：多重磁云、日冕物质抛射、地磁暴、相互作用、行星际空间
[1] Multiple magnetic cloud (Multi-MC), which is formed by the overtaking of successive coronal mass ejections (CMEs), is a kind of complex structure in interplanetary space. Multi-MC is worthy of notice due to its special properties and potential geoeffectiveness. Using the data from the ACE spacecraft, we identify the three cases of Multi-MC in the period from March to April 2001. Some observational signatures of Multi-MC are concluded: (1) Multi-MC only consists of several magnetic clouds and interacting regions between them; (2) each subcloud in Multi-MC is primarily satisfied with the criteria of isolated magnetic cloud, except that the proton temperature is not as low as that in typical magnetic cloud due to the compression between the subclouds; (3) the speed of solar wind at the rear part of the front subcloud does not continuously decrease, rather increases because of the overtaking of the following subcloud; (4) inside the interacting region between the subclouds, the magnetic field becomes less regular and its strength decreases obviously, and (5) b value increases to a high level in the interacting region. We find out that two of three Multi-MCs are associated with the great geomagnetic storms (Dst �� 200 nT), which indicate a close relationship between the Multi-MCs and some intense geomagnetic storms. The observational results imply that theMulti-MC is possibly another type of the interplanetary origin of the large geomagnetic storm, though not all of them have geoeffectiveness. Based on the observations from Solar and Heliospheric Observatory (SOHO) and GOES, the solar sources (CMEs) of these Multi-MCs are identified. We suggest that such successive halo CMEs are not required to be originated from a single solar region. Furthermore, the relationship between Multi-MC and complex ejecta is analyzed, and some similarities and differences between them are discussed. INDEX TERMS: 2111 Interplanetary Physics: Ejecta, driver gases, and magnetic clouds; 1739 History of Geophysics: Solar/planetary relationships; 7513 Solar Physics, Astrophysics, and Astronomy: Coronal mass ejections; 2788 Magnetospheric Physics: Storms and substorms; KEYWORDS: multiple magnetic clouds, coronal mass ejections, geomagnetic storms, interaction, interplanetary space