毫米波活动区及其爆发的某些观测特性

本文分析了1993年11月16日—12月4日期间用青海13.7米射电望远镜(22.235GH_2)观测的毫米波活动区及其爆发的观测特性,得到如下几点结论:1.毫米波活动区出现双极环结构是衰亡的征兆。2.毫米波上的渐升渐降型(GRE)爆发,与H_a耀斑和软X射线爆相关性强,其辐射为热迥旋辐射机制,其爆发源可能在色球高层。3.在GRE爆发上没有观测到毫秒快速精细结构,这与目前分米波的观测结果是一致的。     

对2007年5月23日的一个CME的起源和初始阶段的观测研究

利用多波段联合观测数据,综合分析研究了一个发生于2007年5月23日的日冕物质抛射(Coronal Mass Ejection,CME)爆发事件的起源和初始阶段的物理演化过程.该CME起源于活动区10956内的一个并没有严格地位于活动区极性反转线上的U形活动区暗条,该暗条首先被扰动,然后从中间部分开始缓慢上升.在暗条上升运动过程中,从极紫外和软X射线像上可观测到位于暗条上方的日冕磁环也在不断地上升并且有持续向外的扩张运动.最终,这些冕环和暗条一起爆发并伴随着一个位于暗条断开位置附近的日冕暗化区域的形成.这一爆发过程还伴随着一个静止轨道业务卫星(GeostationaryOperational Environmental Satellites,GOES)软X射线流量级别为B5.3的亚耀斑发生,该光斑显示出与CME之间具有在时间和空间上的紧密联系.与CME的"标准"磁流绳模型一致,这些太阳表面活动可以看作是CME的初始演化阶段在日面上的表现信号,并且该CME的亮前锋可能是由预先存在于暗条上方的冕环体系直接演化而来.另外,文中还讨论了与该事件相关的暗条爆发、耀斑、冕环扩张和消失以及日冕暗化之间的关系.     

AR6659光球色球的磁场速度场的演化特征及其与大耀斑的关系

ＡＲ６６５９是２２周以来最重要的一个活动区，它爆发了２２周最强大的高能事件。本文用云南天文台的光球、色球精细结构照片和北京天文台怀柔站的磁场速度场资料，分析了该活动区磁场速度场的二维位形和大耀斑期间的演化特征。本文分析的４个大耀斑均爆发在中性线附近的Ｎ极区磁场梯度大的地方及色球速度场的红移区。偏带观测也显示耀斑物质是向红端移动的。耀斑波沿横场传播在离本黑子群几万至十几万公里的地方激起感生耀斑，在原生耀斑与感生耀斑之间往往有耀斑环相连。此外，本文还从演化特征出发分析了耀斑爆发前活动区等离子体的宏观不稳定性。     

1988年9—10月各活动区的同极磁流合并与强X射线耀斑

木文对1988年9—10月份各活动区的纵场磁图作了同极磁流合并过程的统计分析,并且证认了与之有关的强X射线耀斑(M、X级耀斑)。结果表明,同极磁流合并是少数(4％)活动区磁场位形出现的演化过程,它的强X射线耀斑的产率很高。     

1986年2月4日太阳耀斑的演化研究

本文根据乌鲁木齐天文站的H_α耀斑及3.2cm射电流量观侧资料、云南天文台的黑子精细结构照相和Marshall Space Flight Center的向量磁场图,对1986年2月4日的六个耀斑的形态相关及演化联系,特别是0736UT 4B/3X大耀斑的发展过程进行了综合分析。主要结果是: 1.4日大耀斑的初始亮点和闪光相的主要形态演化,与活动区中沿中性线新浮现的强大电流/磁环系密切相关。后者的主要标志是沿中性线的长的剪切半影纤维及它两端的偶极旋涡黑子群(1_3F_3)。 2.上述大耀斑与1972年8月4日0624 UT大耀斑爆发的磁场背景及主要形态特征相似,表明两者的储能和触发机制可能相同。 3.大耀斑爆发的H_α初始亮点,双带出现,环系形成,亮物质抛射和吸收冕珥等现象同3.2cm射电流量的变化在时间上有较好的对应关系。 4.重复性的前期小耀斑爆发位置和发展趋势与大耀斑的主要形态及演化特征相似。它们相对于剪切的纵场中性线两侧的位置相近或相同。因而,可以看作上述强大电流/磁环系不稳性发展过程中的前置小爆发。     

2个太阳爆发事件中磁准分界面的演化

磁准分界面(Quasi-Separatrix Layer,简称QSL)是3维磁结构中磁力线连接性发生显著改变的区域,观测表明它多数时候和耀斑带所在的位置符合得较好.有关这一结构和3维磁重联及耀斑关系的研究在近年来受到越来越多的关注.从QSL的理论出发,研究了2011年12月26日在活动区AR11384发生的一个C5.7级典型双带耀斑(事件1)和2015年6月22日发生在活动区AR12371处的一个M6.5级耀斑(事件2).结合SDO/AIA(Solar Dynamics Observatory/Atmospheric Imaging Assembly)观测到的多波段数据和SDO/HMI(Helioseismic and Magnetic Imager)观测到的矢量磁场数据,首先分别利用势场和非线性无力场对日冕的3维磁场结构进行了外推,并计算了活动区磁自由能的演化;然后基于势场和非线性无力场的外推结果计算了不同高度处磁压缩因子(magnetic squashing factor)Q的对数分布,并研究了不同高度磁准分界面与相应高度处观测到的耀斑带的演化关系.最后分析了2个耀斑事件的多波段演化特征,并计算得到事件2中磁力线的平均滑动速度在304?A波段和335?A波段分别为4.6 km·s~(-1)和6.3 km·s~(-1).研究发现:计算得到的磁准分界面在色球和日冕中的位置和相应高度观测到的耀斑带的位置符合得较好,而且各层次的磁准分界面与相应层次的耀斑亮带在时间上也有近乎一致的演化行为,这突显出了磁准分界面理论在3维磁重联和耀斑研究中的作用,并证实事件2耀斑能量的释放可能是通过发生在QSL处的磁重联进行的,同时说明,研究QSL对于理解2维磁重联和3维磁重联本质联系是至关重要的.     

2个二次触发型太阳耀斑的射电时间轮廓及其日冕磁结构

利用国家天文台(北京和昆明)的射电频谱仪(频段为0.65~7.6 GHz)和相关的NoRH/17GHz射电以及TRACE/171 EUV和Yohkoh/SXT的观测资料,分析了2001/04/10和10/19的2个共生精细时间结构的稀有事件,这2个事件的射电爆发时间轮廓和观测特征相似,通过这2个事件的微波(17GHz)偏振观测资料的比较,发现这2个射电爆发均由包含多重(4极)磁结构的复杂活动区引起,特别指出这2个耀斑最后都导致了耀斑后相的分米波射电爆发(第二次触发耀斑),这可能是后环引起的射电爆发。它们都分别对应于双极磁位形,表明这两次触发耀斑是由相似的耀斑模型产生。2个分米波爆发可能是相似(homologous)耀斑的射电表现,可以推测这两次耀斑的驱动器可能皆是磁流浮现或对消(因为源区有新的单或双极出现或消失),而它们的触发器皆是由双极反向Y型位形(具有一个双极拱的单磁流系统)的磁重联,耀斑后环的演化是导致耀斑后相分米波射电爆发的必要条件。我们认为,这双带耀斑对应的宽带射电爆发辐射机制是回旋同步加速辐射过程,而耀斑后相的窄带分米波爆发的辐射机制是等离子体辐射过程。     

AR5229活动区中耀斑和磁场的关系(英文)

本文研究了活动区5229中的H_β耀斑和磁场的关系。所用资料为北京天文台怀柔太阳观测站1988年11月13—18日期间获得的(时值活动区5229位于E40°W40°)。按活动区磁场演化情况,考察了新浮现磁流、磁剪切和磁对消与耀斑形成的关系。 图1a-1f给出了怀柔站观测到的11个H_β耀斑及87个耀斑核在纵向磁图上的情况。磁图以等高斯线形式给出,图中虚线表示负极,实线表示正极,等高斯线由外向内分别为20,40,80,160,320,640,960,1280,1600,1920,2240,2580,2800高斯。黑色小块表示Hβ耀斑核。其中有四分之三的Hβ耀斑核离开极性反变线的距离在10弧秒之内。发生在该活动区的耀斑超过80个,而怀柔站观测的仅是很小一部分。这对于耀斑建立过程的研究是很不够的,必需补充其他天文台的资料。注意到周报上已列出该活动区的软X射线(1～8A)M1.0级以上的高能耀斑事件,将它们补充进图1,用黑色三角形表示,画其位置时考虑到耀斑、黑子及磁特征之间的关系和它们彼此之间的时间差,并按Howard和Harvey给出的较差自转公式进行了改正。10个高能耀斑事件中有6个可能与磁特征N_3,N_7和P_2的衰减(即对消,另一极性在复杂活动区中衰减不明显)有关;另外的事件可能与发生在磁特征N_2、P_2之间的磁剪切有关。     

1993年10月2日耀斑的Hα,微波和硬X射线暴的综合分析

本文介绍1993年10月2日发生的一个1N／C6.5级耀斑多波段观测的结果．综合比较了耀斑的单色象，Hα波段工维光谱，2840兆赫微波爆发和硬X射线爆发资料．得到Hα单色象上不同亮核的强度变化，与微波及硬X射线暴的时间轮廓比较，给出了色球耀斑区亮度场的演化，对照磁图确定了耀斑区的磁场位形，从而对该耀斑产生和加热提出了一种可能的解释．     

太阳活动区同极磁流合并与高能耀斑

本文对六个活动区的同极磁流合并现象进行了分析,同极磁流合并可以分为两类。一类是在同极磁流合并之前,其间的异极性磁流很弱,它们的合并不是由于互相靠近而是由于相对延伸,另一类是在合并之前,其间有较强的异极性磁流,合并后有的明显靠近,有的则看不到靠近现象。高能耀斑与同极磁流合并有密切关系。6个活动区中发生的同极磁流合并几乎都与高能耀斑有关,这个结果可用于M和X级X射线耀斑的预报。文中还给出了用于预报的同极磁流合并的定义。     

A Pair of Conjugate Current Ribbons Coinciding with the Double-ribbon Flare

Using the vector magnetograms observed by SDO (Solar Dynamics Observatory)/HMI (Helioseismic and Magnetic Imager), the current distribution and evolution associated with an X9.3 flare occurred in the active region AR12673 on Sept. 6, 2017 are studied in detail. The results show that there is a pair of electric current ribbons with opposite directions and the magnitude of 0.4 A/m${}^2$, which can be called a pair of conjugate electric current ribbons. This pair of conjugate electric current ribbons exist before, during, and after the flare; their positions are almost coincident with the two bright ribbons of the flare, and their shapes are also extremely similar with them. The light curve of the total electric current intensity on Sept. 6 shows that the electric current intensity enhanced sharply during the strong X9.3 flare eruption, and this phenomenon persisted for several hours. The results of this study strongly support the model of QSL (Quasi-Separatrix Layer) 3D magnetic reconnection.     

Magnetic reconnection,electric field,and particle acceleration in the July 14, 2000 solar flare

A topological model with magnetic reconnection at two separators in the corona is used to account for the recently discovered changes of the photospheric magnetic field in the active region NOAA 9077 during the July 14, 2000 flare. The model self-consistently explains the following observed effects: (1) the magnetic field strength decreases on the periphery of the active region but increases in its inner part near the neutral line of the photospheric magnetic field; (2) the center-of-mass positions of the fields of opposite (northern and southern) polarities converge; and (3) the magnetic flux of the active region decreases after the flare. The topological model gives not only a qualitative interpretation of the flare phenomena (the structure of the interacting magnetic fluxes in the corona, the location of the energy sources, the shape of the flare ribbons and kernels in the chromosphere and photosphere), but also correct quantitative estimates of the large-scale processes that form the basis for solar flares. The electric field emerging in the flare during large-scale reconnection is calculated. The electric field strength correlates with the observed intensity of the hard X-ray bremsstrahlung, suggesting an electron acceleration as a result of reconnection.     

Horizontal flows concurrent with an X2.2 flare in the active region NOAA 11158

Horizontal proper motions were measured with local correlation tracking (LCT) techniques in active region NOAA 11158 on 2011 February 15 at a time when a major (X2.2) solar flare occurred. The measurements are based on continuum images and magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The observed shear flows along the polarity inversion line were rather weak (a few 100 m s^–1). The counter‐streaming region shifted toward the north after the flare. A small circular area with flow speeds of up to 1.2 km s^–1 appeared after the flare near a region of rapid penumbral decay. The LCT signal in this region was provided by small‐scale photospheric brigthenings, which were associated with fast traveling moving magnetic features. Umbral strengthening and rapid penumbral decay was observed after the flare. Both phenomena were closely tied to kernels of white‐light flare emission. The white‐light flare only lasted for about 15 min and peaked 4 min earlier than the X‐ray flux. In comparison to other major flares, the X2.2 flare in active region NOAA 11158 only produced diminutive photospheric signatures (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic field, helicity and the 2000 July 14 flare in solar active region 9077

In this paper we analyse the non-potential magnetic field and the relationship with current (helicity) in the active region NOAA 9077 in 2000 July, using photospheric vector magnetograms obtained at different solar observatories and also coronal extreme-ultraviolet 171-Å images from the TRACE satellite.
We note that the shear and squeeze of magnetic field are two important indices for some flare-producing regions and can be confirmed by a sequence of photospheric vector magnetograms and EUV 171-Å features in the solar active region NOAA 9077. Evidence on the release of magnetic field near the photospheric magnetic neutral line is provided by the change of magnetic shear, electric current and current helicity in the lower solar atmosphere. It is found that the 'Bastille Day' 3B/5.7X flare on 2000 July 14 was triggered by the interaction of the different magnetic loop systems, which is relevant to the ejection of helical magnetic field from the lower solar atmosphere. The eruption of the large-scale coronal magnetic field occurs later than the decay of the highly sheared photospheric magnetic field and also current in the active region.     

Solar Flare Activity and Variability of Electric Current Helicity

1 INTRODUCTIONRecently Bao, Zhang, Ai, and Zhang (1999), using Huairou vector magnetograph data,have shown that the average current helicity (h.) or the curreflt helicity imbalance ph of activeregions change rapidly after so1ar flares. Up'an the onset of flares it tends to decrease for a fewhours and then to increase again, whereas ifQ some cases the flare promotes an increase in thecurrent helicity The observations led to tbe fol1owing conclusions: (1) raPid and substantialchanges of c…     

A comparison between magnetic shear and flare shear in a well-observed M-class flare

We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our empha-sis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse mag-netic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena.     

Flare ribbon expansion and energy release

We report a detailed examination about the relationship between the evolution of the Hα flare ribbons and the released magnetic energy during the April 10 2001 flare. In the Hα images, several bright kernels are observed in the flare ribbons. We identified the conjugated foot-points, by analyzing the lightcurves at each Hα kernels, and showed their connectivities during the flare. Then, based on the magnetic reconnection model, we calculated quantitatively the released energy by using the photospheric magnetic field strengths and separation speeds of the Hα flare ribbons. Finally, we examined the downward motions which are observed at the Hα kernels. We found that the stronger the red-asymmetry tends to be associated with the brighter the Hα kernel.     

Extremely energetic 4B/X17.2 flare and associated phenomena

We observed 4B/X17.2 flare in Hα from super-active region NOAA 10486 at ARIES, Nainital. This is one of the largest flares of current solar cycle 23, which occurred near the Sun’s center and produced extremely energetic emission almost at all wavelengths from γ-ray to radio-waves. The flare is associated with a bright/fast full-halo earth directed CME, strong type II, type III and type IV radio bursts, an intense proton event and GLE. This flare is well observed by SOHO, RHESSI and TRACE. Our Hα observations show the stretching/de-twisting and eruption of helically twisted S shaped (sigmoid) filament in the south-west direction of the active region with bright shock front followed by rapid increase in intensity and area of the gigantic flare. The flare shows almost similar evolution in Hα, EUV and UV. We measure the speed of Hα ribbon separation and the mean value is ∼ 70 km s^-1. This is used together with photospheric magnetic field to infer a magnetic reconnection rate at three HXR sources at the flare maximum. In this paper, we also discuss the energetics of active region filament, flare and associated CME.     

Large-Scale Electric Fields in Solar Flare Regions

A method of separating electric field in the flare region in the potential and vortex (induced) parts is discussed. According to the proposed model, the motion of flare ribbons from the central line of the flare region is caused by the vortex component of the coronal electric field, while the motion of bright spots within the flare region towards the central line is driven by the potential component of that field. The intensity of both the components of the flare region electric field is estimated to equal approximately 1–3 V cm^–1, which provides the input of the electromagnetic energy into the active region at a rate of about 10¹⁰ erg cm^–2 s^–1.