James A W, Green L M, Palmerio E, Valori G, Reid H A S, Baker D, Brooks D H, van Driel-Gesztelyi L, Kilpua E K J
1Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT UK.
2Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland.
Sol Phys. 2017;292(5):71. doi: 10.1007/s11207-017-1093-4. Epub 2017 May 1.
Coronal mass ejections (CMEs) are one of the primary manifestations of solar activity and can drive severe space weather effects. Therefore, it is vital to work towards being able to predict their occurrence. However, many aspects of CME formation and eruption remain unclear, including whether magnetic flux ropes are present before the onset of eruption and the key mechanisms that cause CMEs to occur. In this work, the pre-eruptive coronal configuration of an active region that produced an interplanetary CME with a clear magnetic flux rope structure at 1 AU is studied. A forward-S sigmoid appears in extreme-ultraviolet (EUV) data two hours before the onset of the eruption (SOL2012-06-14), which is interpreted as a signature of a right-handed flux rope that formed prior to the eruption. Flare ribbons and EUV dimmings are used to infer the locations of the flux rope footpoints. These locations, together with observations of the global magnetic flux distribution, indicate that an interaction between newly emerged magnetic flux and pre-existing sunspot field in the days prior to the eruption may have enabled the coronal flux rope to form via tether-cutting-like reconnection. Composition analysis suggests that the flux rope had a coronal plasma composition, supporting our interpretation that the flux rope formed via magnetic reconnection in the corona. Once formed, the flux rope remained stable for two hours before erupting as a CME.
The online version of this article (doi:10.1007/s11207-017-1093-4) contains supplementary material, which is available to authorized users.
日冕物质抛射（CMEs）是太阳活动的主要表现形式之一，会引发严重的空间天气效应。因此，努力实现对其发生的预测至关重要。然而，CME形成和爆发的许多方面仍不清楚，包括在爆发开始前是否存在磁通量绳以及导致CME发生的关键机制。在这项工作中，研究了一个活动区的爆发前日冕结构，该活动区产生了一个在1天文单位处具有清晰磁通量绳结构的行星际CME。在爆发开始前两小时（SOL2012 - 06 - 14），极紫外（EUV）数据中出现了一个前向S型西格玛，这被解释为爆发前形成的右手磁通量绳的特征。耀斑带和EUV暗化被用于推断磁通量绳脚点的位置。这些位置，连同全球磁通量分布的观测结果，表明在爆发前几天新出现的磁通量与先前存在的黑子场之间的相互作用可能通过类似系绳切断的重连使得日冕磁通量绳得以形成。成分分析表明磁通量绳具有日冕等离子体成分，支持了我们关于磁通量绳通过日冕中的磁重连形成的解释。一旦形成，磁通量绳在作为CME爆发前保持稳定两小时。
本文的在线版本（doi:10.1007/s11207 - 017 - 1093 - 4）包含补充材料，授权用户可获取。
