Despite extensive research on various global waves in solar eruptions, debate continues on the intrinsic nature of them. In this work, we performed numerical experiments of the coronal mass ejection with emphases on the associated large-scale MHD waves. A fast-mode shock forms in front of the flux rope during the eruption with a dimming region following it, and the development of a three-component structure of the ejecta is observed. At the flank of the flux rope, the slow-mode shock and the velocity vortices are also invoked. The dependence of the eruption energetics on the strength of the background field and the coronal plasma density distribution is apparent： the stronger the background field is, and/or the lower the coronal plasma density is, the more energetic the eruption is. In the lower Alfven speed environment, the slow mode shock and the large scale velocity vortices may be the source of the EIT wave. In the high Alfvdn speed environment, on the other hand, the echo due to the reflection of the fast shock on the bottom boundary could be so strong that its interaction with the slow mode shock and the velocity vortices produces the second echo propagating downward and causing the secondary disturbance to the boundary surface. We suggest that this second echo, together with the slow shock and the velocity vortices, could constitute a possible candidate of the source for the EIT wave.
区域生长法是一种基于区域分割的算法,其关键在于种子点的准确提取和生长准则的定义。用区域生长法对云南天文台澄江1 m红外太阳塔望远镜(New Vacuum Solar Telescope,NVST)在TiO(705.8nm)波段的观测资料进行分析识别,采用拉普拉斯算子提取种子点,然后用图像灰度阈值作为生长准则对种子点进行生长,最后剔除误识别的米粒,从而完成对磁亮点的识别工作。然后又对Hinode的观测资料进行了识别并与Utz等人的结果进行对比。
During the total solar eclipse of July 22, 2009, we carried out a white-light observation in Anji, Zhejiang, China. The aim wasto observe the polar plumes (PPs) with high spatial and temporal resolutions in white-light. With the observational data, weinvestigate the properties and evolution of the PPs and compare them with those of the low-latitude plumes (LPs). We find thatboth the PPs and the LPs have comparable lengths and widths, and the mean length and width are 300 Mm and 16 Mm, re-spectively. The average inclination angle (13 degree) of the PPs is smaller than that (32 degree) of the LPs. Generally, theplumes which are closer to the coronal hole center are more vertical. We trace the PPs and the LPs in the sequence of imagesand find that none of them disappears and no new one is created. Additionally, neither plasma outflow nor transverse oscilla-tion is observed. These imply that the evolution process of plumes is much longer than the timescale of eclipse.
It is well known that some coronal jets exhibit helical structures and un- twisting. We attempt to inspect the origin of twist in a blowout jet. By means of multiwavelength and multi-angle observations from Solar Dynamics Observatory （SDO） and Solar Terrestrial Relations Observatory-Ahead （STEREO-A）, we firstly report a polar untwisting jet that is a blowout jet which leads to a jet-like coronal mass ejection. From the viewpoint of SDO, the jet shows clear untwisting behavior and two jet-spires. However, from the viewpoint of STEREO-A the jet actually comes from the whiplike prominence eruption and is followed by a white-light jet. Our observations indicate that twist in blowout jets may result from the erupting mini-prominences/mini- filaments in the jet base.
Jun-Chao HongYun-Chun JiangJia-Yan YangRui-Sheng ZhengYi BiHai-Dong LiBo YangDan Yang
太阳活动会引起输变电系统异常,特别是对超长距离输变电系统的危害尤其明显.根据SOHO/LASCO(Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph)的日冕物质抛射(Coronal Mass Ejection,CME)数据、华北电力大学和芬兰气象研究所获得的地磁感应电流(Geomagnetically Induced Current,GIC)数据以及地磁暴数据,分析研究了与GIC事件有关的对地晕状CME的重要观测特征和物理性质.按照对称性将晕状CME进行分类后,发现造成GIC事件的晕状CME主要有3类:完全对称型、亮度不对称型和外形不对称型.不同类型的全晕状CME驱动的GIC事件在强度、持续时间等方面特征各不相同.其中,亮度不对称型晕状CME很有可能对GIC事件影响最为严重.同时注意到GIC与地磁场随时间的变化率也具有较好的相关性.
