Large-Scale Activity in the Bastille Day 2000 Solar Event
Large-Scale Activity in the Bastille Day 2000 Solar Event
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DOI：
10.1007/s11207-005-3654-1
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发表时间：
2005-06
期刊：
影响因子：
2.8
通讯作者：
I. Chertok;V. Grechnev
中科院分区：
文献类型：
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作者：
I. Chertok;V. Grechnev
我们使用 EUV 望远镜 SOHO/EIT 生成的图像分析了 2000 年 7 月 14 日著名事件中的变暗（即亮度暂时降低的区域）和日冕波的表现。我们的分析受到 Andrews (2001, Solar Phys.204, 181 (Paper I)) 的一篇论文的启发，其中使用 195 Å 的游动差分 EIT 图像来研究该事件，该图像是通过从每个当前图像中减去先前图像而形成的。此类图像强调了在两个后续日光图之间的 12 分钟间隔内所观察到的结构的亮度、位置和配置的变化。然而，它们扭曲了日冕物质抛射引起的大规模干扰的图像，特别是变暗。调光的真实图片可以从基于固定的差异“去旋转”图像获得。后者分两个阶段形成：首先，使用所有图像的三维旋转（“去旋转”）到事件前日光图的时间（此处为世界标准时间 10:00）来补偿太阳自转，然后从所有其他日光图中减去基础日光图。我们发现真实的调光与安德鲁斯（论文 I）所描述的调光有本质上的不同。与日冕物质抛射有关的日冕中大规模磁场的重组伴随着两次大调暗的出现和增长。其中一处位于喷发中心以南的中央经线上，喷发前拱廊处。另一次变暗占据了耀斑区域和遥远的西部活动区域之间的空间。事实上，在整个太阳盘上，特别是在西北象限内，都观察到了几次较小的变暗。我们还在北极地区发现了具有日冕波特性的传播扰动，但没有观察到变暗。这一事实是在调光和日冕波之间可能存在关联的背景下讨论的。抑制了 EIT 图像中高能粒子产生的“暴风雪”后，我们考虑了 171、195、284 和 304 Å 的所有四个 EIT 通带中的调光表现，以及主要调光的光变曲线，包括后来的几张 195 Å 图像。我们的分析表明，调暗的主要原因是密度损耗，在本次事件中密度损耗高达 30%。变暗的图片表明，巴士底日事件中的日冕物质抛射是由一些磁绳组成的章鱼状束，其“手臂”连接到几乎整个可见太阳表面上的几个活动区域。
We have analyzed dimmings, i.e., regions of temporarily reduced brightness, and manifestations of a coronal wave in the famous event of 14 July 2000 using images produced with the EUV telescope SOHO/EIT. Our analysis was inspired by a paper by Andrews (2001,Solar Phys.204, 181 (Paper I)), in which this event was studied usingrunning-difference EIT images at 195 Å formed by subtraction of a previous image from each current one. Such images emphasize changes of the brightness, location, and configuration of observed structures occurring during the 12-min interval between two subsequent heliograms. However, they distort the picture of large-scale disturbances caused by a CME, particularly, dimmings. A real picture of dimmings can be obtained fromfixed-basedifference ‘de-rotated’ images. The latter are formed in two stages: first, the solar rotation is compensated using three-dimensional rotation of all images (‘de-rotation’) to the time of a pre-event heliogram, here 10:00 UT, and then the base heliogram is subtracted from all others. We show real dimmings to be essentially different from those described by Andrews (Paper I). The restructuring of large-scale magnetic fields in the corona in connection with the CME was accompanied by the appearance and growth of two large dimmings. One of them was located along the central meridian, southward of the eruption center, at the place of the pre-eruption arcade. Another dimming occupied the space between the flare region and a remote western active region. Several smaller dimmings were observed virtually over the whole solar disk, especially, within the northwest quadrant. We have also revealed a propagating disturbance with properties of a coronal wave in the northern polar sector, where no dimmings were observed. This fact is discussed in the context of probable association between dimmings and coronal waves. Having suppressed the ‘snowstorm’ produced in the EIT images by energetic particles, we have considered dimming manifestations in all four EIT pass bands of 171, 195, 284, and 304 Å as well as the light curves of the main dimmings including several later images at 195 Å. Our analysis shows that the major cause of the dimmings was density depletion that reached up to 30% in this event. The picture of dimmings implies that the CME in the Bastille Day event was an octopus-like bundle of some magnetic ropes, with the ‘arms’ being connected to several active regions disposed over almost the whole visible solar surface.