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。     

AR5395:精细结构,磁剪切和耀斑

用26cm太阳望远镜的高分辨光球色球照片和北京夭文台怀柔站的太阳磁图证认出AR5395活动区中5段剪切的磁极性反转线(中性线)。考察这些线段与黑子精细结构,活动区暗条以及耀斑活动之间的关系。结果表明,多数观测到的耀斑发生在磁剪切     

AR5629:1989年8月17日耀斑环的观测

利用怀柔太阳磁场望远镜,我们观测到1989年8月17日出现在太阳西边缘的耀斑环,它们产生在AR5629上(S17,L74)。当时,该活动区已转到日背面,约10°左右。17日,从UT0132至UT0911,我们取得了该耀斑环的一系列Hβ单色光资料(图1)和它们的二维实时视向速度场(图2)。从观测中,我们可以看到环的形成演化的全     

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.     

活动区NOAA 6891的耀斑分析

本文分析了１９９１年１０月的一个大δ型活动区的黑子演化和耀斑产生的位置及可能原因，发现该活动区８９％的耀斑产在两个磁中性线旁，两磁中性线处皆有较大的磁横场和剪切。在Ｈα中一中性线处观测到暗条由于黑子的挤压运动而变得剪切成“Ω”型；另一中性线处观测到纤维束较大的变化，有时明显能观测到磁绳结构。     

太阳宁静区小尺度磁场的二维功率谱(英文)

以1988年9月5日北京天文台怀柔太阳观测站高分辨率和高灵敏度磁强图为基础,首次给出了对一太阳宁静区小尺度磁场空间分布的二维功率谱。 尽管从总体上,功率谱的分布呈现从低频分量向高频分量迅速衰减的趋势,但是,反映小尺度磁场分布的不同尺度空间周期性的分离的尖峰,是功率谱的最主要特征。 本文的主要结果可概括为下列两点: (1)太阳宁静区的磁通量不仅凝聚在分离的、具有相对较强磁通量密度的磁结构内,而且磁结构的空间分布也呈现分离的尺度不同的周期。 (2)小尺度磁场空间分布的最显著的周期,具有超米粒的空间尺度。这与以往磁对流理论与有关观测结果相一致。在功率谱中,还可以证认相应于亚超米粒,及亚超米粒和超米粒之间尺度的空间周期的大量尖峰。这是本文首次得到的。 包含更多观测资料的进一步工作是必须的,特别是获得对同一宁静区的速度场和磁场同时性的二维功率谱,对研究磁场和对流速度场的相互作用是有重要意义的。观测的功率谱与理论预测谱的比较,将有助于理解太阳光球分离磁结构形成的物理过程。     

太阳的磁绳暗条和一个Ⅲb级耀斑

2000年9月14－18日在紫金山天文台赣榆观测站观测到太阳上有一个中小型活动区，黑子面积不大，但有一个奇特的活动区暗条，16日产生了一个Ⅲb级耀斑，有较强的地球物理效应。计算该区的磁结构，结果发现此磁绳状暗条与磁中性线附近低磁弧系相关，磁场在磁绳附近有强剪切，QSL分析显示三维磁重联能够在暗条附近出现，这可解释大耀斑的形成。     

大型太阳活动区磁场的一个模型

用时间缓变的非线性无力场模拟超级活动区（弧岛式大型δ黑子）的磁场位形。这个复杂磁场包含了向量磁场的主要观测特征：正负磁流极端不平衡性（正负磁流之比为１：６）,Ｕ形磁反变线,局域磁场的二极子、四极子差异性。模拟结果厅用来解释一些观测结果：（１）大耀斑主要产生在Ｕ形中性线的磁性混杂区或四极子区（２）Ｕ形反变线的准双极性区几乎没有大耀斑很小。（３）活动区内部的大型旋转运动和磁沲运动会导致四极子场磁拓扑分     

与耀斑双带重合的一对共轭电流带

利用SDO (Solar Dynamics Observatory)/HMI (Helioseismic and Magnetic Imager)观测到的矢量磁图,研究了与活动区AR12673上爆发的一个X9.3级耀斑(2017年9月6日)的相关电流分布和演化.结果显示,在该活动区的磁中性线两边存在一对方向相反的电流密度约为0.4 A/m~2的长电流带,可称其为一对共轭电流带.这对共轭电流带在耀斑发生之前、期间以及之后一直存在;并且观测到,该耀斑的两个亮带的位置几乎刚好与两个电流带重叠,它们的形状也极其相似. 9月6日电流总强度演化曲线表明,电流强度在X9.3级强耀斑爆发期间出现快速增加的现象,这种现象持续了几个小时.这一研究结果有力支持了磁准分界面(Quasi-Separatrix Layer, QSL) 3维重联模型.     

新浮磁流与增亮事件

本文利用阳光卫星的软Ｘ 射线资料,日本国立天文台的Ｈα单色像和相对应的北京天文台怀柔站的活动区矢量磁场资料及美国基特峰天文台的全日面磁图,对发生在１９９４ 年５ 月１８ 日的软Ｘ 射线和Ｈα增亮事件进行了仔细的研究。研究表明增亮事件明显与新浮剪切磁流出现相关,Ｈα和软Ｘ 射线亮点的投影位置正好位于新浮小磁流环的三个足点之间,同时亮点也位于分界面与光球面的交线附近,故该增亮事件也许是太阳低层大气磁重联的观测证据     

A new technique of observing the magnetic field of solar active regions

By fitting a new type of polarization detector after the entrance slit of a solar spectrograph, the two dimensional magnetic field of solar active regions can be obtained. Not only the field intensity, but also the longitudinal map is obtained quickly. The simultaneous observation of a few lines will also provide data on the structure of the magnetic tubes etc.     

太阳磁场观测研究

简要回顾了近几年国际上太阳磁场研究的一些重要进展，包括耀斑与磁切和电流的关系，电流螺度和磁螺度，磁场拓扑性，三维磁场外推，色球磁场研究，日冕磁场研究，内网络磁元，磁流和振荡，极区磁场观测以及色球磁元观测等方面内容，同时也介绍了怀柔太阳观测站最近所取得的主要成果，自20世纪90年代以来，YOHKOH高分辨率的太阳X射线数据，SOHO的多波段大尺度观测，TRACE的高分辨太阳过渡区资料，为研究太阳磁场从内部到距离几十太阳半径处的大范围演化提供了依据，高效的空间资料结合长期的地面资料，将是正派推动太阳磁场研究的重要手段和必然趋势。     

Structure and evolution of magnetic fields associated with solar eruptions

This paper reviews the studies of solar photospheric magnetic field evolution in active regions and its relationship to solar flares. It is divided into two topics, the magnetic structure and evolution leading to solar eruptions and rapid changes in the photospheric magnetic field associated with eruptions. For the first topic, we describe the magnetic complexity, new flux emergence, flux cancelation, shear motions, sunspot rotation and magnetic helicity injection, which may all contribute to the storage and buildup of energy that trigger solar eruptions. For the second topic, we concentrate on the observations of rapid and irreversible changes of the photospheric magnetic field associated with flares, and the implication on the restructuring of the three-dimensional magnetic field. In particular, we emphasize the recent advances in observations of the photospheric magnetic field, as state-of-the-art observing facilities(such as Hinode and Solar Dynamics Observatory) have become available. The linkages between observations, theories and future prospectives in this research area are also discussed.     

CMOS图像传感器在太阳磁场观测中的应用研究

磁场是太阳物理的第1观测量,当前太阳磁场观测研究正迈向大视场、高时空分辨率、高偏振测量精度以及空间观测的时代.中国首颗太阳观测卫星—先进天基太阳天文台(ASO-S)也配置了具有高时空分辨率、高磁场灵敏度的全日面矢量磁像仪(FMG)载荷,针对FMG载荷的需求,讨论了大面阵、高帧频互补金属氧化物半导体(Complementary Metal Oxide Semiconductor, CMOS)图像传感器应用于太阳磁场观测的可行性.首先,基于滤光器型太阳磁像仪观测的原理,比较分析了目前CMOS图像传感器(可用的或是可选的两种快门模式)的特点,指出全局快门类型更适合FMG;其次搭建了CMOS传感器实验室测试系统,测量了CMOS图像传感器的像素增益及其分布规律;最后在怀柔太阳观测基地的全日面太阳望远镜上开展了实测验证,获得预期成果.在这些研究基础上,形成了FMG载荷探测器选型方向.     

Magnetic field lines for a flux tube

Equations for the magnetic field components in a two dimensional cylindrically symmetric flux tube equilibrium have been derived and, in a simple case, solved. The resulting magnetic configuration possesses a strong magnetic field in a thin tube below a reference level (solar photosphere). Above this reference level the field lines spread out in all directions.     

A Comparison Between Nonlinear Force-Free Field and Potential Field Models Using Full-Disk SDO/HMI Magnetogram

Measurements of magnetic fields and electric currents in the pre-eruptive corona are crucial to the study of solar eruptive phenomena, like flares and coronal mass ejections (CMEs). However, spectro-polarimetric measurements of certain photospheric lines permit a determination of the vector magnetic field only at the photosphere. Therefore, there is considerable interest in accurate modeling of the solar coronal magnetic field using photospheric vector magnetograms as boundary data. In this work, we model the coronal magnetic field above multiple active regions with the help of a potential field and a nonlinear force-free field (NLFFF) extrapolation code over the full solar disk using Helioseismic and Magnetic Imager (SDO/HMI) data as boundary conditions. We compare projections of the resulting magnetic field lines with full-disk coronal images from the Atmospheric Imaging Assembly (SDO/AIA) for both models. This study has found that the NLFFF model reconstructs the magnetic configuration closer to observation than the potential field model for full-disk magnetic field extrapolation. We conclude that many of the trans-equatorial loops connecting the two solar hemispheres are current-free.     

实时相关跟踪图像处理系统

文章介绍了怀柔太阳观测基地最近完成的一套实时高分辨太阳磁场观测系统。系统采用局部相关跟踪算法来提高磁场观测数据的空间分辨率，同时对相关跟踪算法的实现程序进行了优化以满足常规太阳磁场观测的要求。通过对试观测和常规观测数据的分析，我们发现：1）该系统能够大大提高单色像、磁场数据的对比度和空间分辨率；2）对相关跟踪算法的优化大大提高了系统的时间分辨率，系统可以投入常规观测使用。     

Large-scale Structure of the Chromospheric Doppler Velocities on the Solar Disk from 2D-spectroscopy within the He I 10830 Å Line

A distribution map of the large-scale chromospheric Doppler velocities on the solar disk for 5 June 2002 is presented. The map was obtained using a 2D-spectroscopy technique within the He?i 10830 Å line. The spatial resolution of the map is about 30 arc sec. The map demonstrates a downflow in the chromosphere over active regions, especially significant around the spots and inside the plages. Positive Doppler velocities correspond to strong magnetic field areas, regardless of the field sign. Three major chromospheric outflow zones are observed: an equatorial and two polar ones. Each area of substantial negative Doppler velocities matches a zone of weak intensity of inner corona observed within the Fe?ix-x 171 Å line by the SOHO spacecraft. A Doppler velocity histogram and the dependence of the Doppler velocities on the cosine of the heliocentric angle for the solar disk are calculated. The total mass outflow from the upper chromosphere is estimated as 2×10¹³ g s^?1. Four percent of this amount is sufficient to produce the fast solar wind.

     

Mapping Solar Wind Streams from the Sun to 1 AU: A Comparison of Techniques

A variety of techniques exist for mapping solar wind plasma and magnetic field measurements from one location to another in the heliosphere. Such methods are either applied to extrapolate solar data or coronal model results from near the Sun to 1 AU (or elsewhere), or to map in-situ observations back to the Sun. In this study, we estimate the sensitivity of four models for evolving solar wind streams from the Sun to 1 AU. In order of increasing complexity, these are: i) ballistic extrapolation; ii) ad hoc kinematic mapping; iii) 1-D upwinding propagation; and iv) global heliospheric MHD modeling. We also consider the effects of the interplanetary magnetic field on the evolution of the stream structure. The upwinding technique is a new, simplified method that bridges the extremes of ballistic extrapolation and global heliospheric MHD modeling. It can match the dynamical evolution captured by global models, but is almost as simple to implement and as fast to run as the ballistic approximation.     

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.