基于深度学习的太阳活动区检测与跟踪方法研究

太阳活动区是各类太阳活动的主要能量来源,剧烈的太阳活动直接影响人类的生存环境,因此,准确地检测与跟踪太阳活动区对监控和预报空间天气非常重要。基于深度学习框架的YOLOv3-spp和DeepSort,提出了一种太阳活动区检测和跟踪方法(Active Regions Detection and Tracking Method, ARDTM),该方法较好地解决了传统图像处理方法易将一个太阳活动区误检测为多个,或者多个太阳活动区误检测为一个的问题;及时捕获新产生的太阳活动区和终止跟踪消失的太阳活动区,有效提高了太阳活动区的跟踪准确率。实验结果表明,该方法可以较好地检测和跟踪不同望远镜、不同时间间隔序列图像中的太阳活动区。     

基于SIFT特征检测和密度峰值聚类的太阳活动区自动检测算法研究

太阳活动区是太阳大气中产生各种活动现象的区域,精确地检测和识别太阳活动区对理解太阳磁场的形成机制具有极为重要的科学意义.根据太阳活动区结构较为复杂的特点,基于尺度不变特征变换(ScaleInvariant Feature Transform, SIFT)和密度峰值聚类(Clustering by Fast Search and Find of Density Peaks,DPC)算法的优越性,提出了一种太阳活动区的自动检测和识别方法.首先,对太阳动力学天文台(Solar Dynamics Observatory, SDO)日震和磁场成像仪(Helioseismic and Magnetic Imager, HMI)的纵向磁图进行对比度增强;然后采用SIFT方法提取出全日面磁图中的特征点;最后利用DPC算法将特征点进行聚类,从而自动检测和识别出太阳活动区.研究结果表明, SIFT和DPC算法相结合的方法可以在不需要人工交互的情况下准确地自动检测出太阳活动区.     

研究人员的好参考书、研究生入门的好教材——《太阳活动区物理》

专著<太阳活动区物理>最近由南京大学出版社出版和发行.该专著由作者,南京大学方成院士、丁明德教授和陈鹏飞教授,以多年来的太阳物理学研究和指导研究生的科研为基础,并结合国内外太阳物理学最新研究成果编写而成的,主要阐述了研究太阳活动区和各种太阳活动现象的观测事实、基本理论、基本方法和主要研究成果.     

冕洞边界区磁结构的探讨—Ⅱ.太阳活动20,21周的冕洞及其边界区磁结构的变

本文分析讨论了太阳活动２０、２１周的冕洞及其边界区磁结构的变化，它包括：冕洞区光球磁场强度、磁极性的变化；冕洞面积与高速太阳风风速的关系，冕洞边界周围的环境，重点探讨太阳活动下降，极小相低纬，赤道冕洞区与其边界区磁结构的变化。     

冕洞边界区磁结构的探讨──Ⅱ．太阳活动20、21周的冕洞及其边界区磁结构的变化

本文分析讨论了太阳活动２０、２１周的冕洞及其边界区磁结构的变化。它包括：冕洞区光球磁场强度、磁极性的变化；冕洞面积与高速太阳风风速的关系；冕洞边界周围的环境。重点探讨太阳活动下降、极小相低纬、赤道冕洞区与其边界区磁结构的变化。     

基于日球物理学事件知识库的太阳活动识别

太阳图像中包含明显的太阳活动区域,以及无现象的太阳宁静区。从太阳图像中识别有效的太阳活动区域,是图像处理技术在天文研究中的典型应用。得益于美国太阳动力学天文台的日球物理学事件知识库提供的实时太阳观测数据,提出了一种基于日球物理学事件知识库的太阳活动识别方法。此方法获取6种太阳活动的信息(发生时间、位置、区域面积),建立对应时间的全日面图像的尺度变换模型。结合位置与区域面积信息,对不同太阳活动进行梯度阈值分割,边界识别方法被用来定位和识别太阳活动的区域。然后,对太阳图像特征参数相关性的研究,得到每种太阳活动的最佳特征参数组合。方法实现了对太阳活动的精确定位和有效识别,为后续工作的开展提供了便利。此外,对不同太阳活动区域提取特定组合的特征,可以为基于内容的图像检索系统建立精简的图像特征集提供一种可行办法。     

太阳活动区的自动观测方法及程序设计

本文提出了用计算机技术对太阳活动区进行自动观测的方法,并着重介绍了所设计的自动观测系统程序。     

太阳活动区纵向电流计算的一个新方法

本文建议了一个用于太阳活动区纵向电流计算的新方法，讨论了将该方法用于向量磁场观测分析的可行性。     

太阳活动区活动性的模糊预测

运用模糊数学的理论和方法对太阳活动区的活动性进行了预测。为了综合评估和预测活动区的活动性，根据耀斑与黑子群特征因子间的关系，构造了隶属函数。通过数据处理与分析，得到了对活动区活动性较好的预测结果，预测的准确性＞95%。已成功编制了太阳活动预报的数据处理实用软件，根据黑子群的特征因子值，即刻就能得到活动区活动性的预报结果，预测结果表明模糊综合评估方法能很好地预报太阳活动。     

编辑说明

中国科学院数学物理学部召集的“太阳活动区光学、射电形态分析会”于1981年8月21日—9月2日在昆明云南天文台召开,13个单位的代表和特邀代表共36人参加了会议。会议收到各种报告和论文(或提要)共50篇,其中关于太阳活动区和耀斑的形态描述及分析报告的文章24篇,有关观测仪器和观测方法的工作报告、理论探讨的文章14篇,有     

Variations of magnetic fields and electric currents associated with a solar flare

The high-resolution vector magnetograms obtained with the solar telescope magnetograph of the Beijing Astronomical Observatory of the active region AR 4862 on 7 October, 1987, close before and after a solar flare, were used to calculate the electric current densities in the region. Then the relations between the flare and the magnetic fields as well as the electric currents were studied. The results are: (i) the transverse magnetic fields, and hence the longitudinal electric currents in the region before and after the flare, are evidently different, while the longitudinal magnetic fields remain unchanged; (ii) this confirms the result obtained previously that the flare kernels coincide with the peaks of longitudinal electric density in active regions; (iii) the close relation between the flare kernels and the electric currents indicates that the variations of the transverse magnetic fields and the longitudinal electric currents arise not from the general global evolution of the active region, but from the flare. These results tend to the conclusion that the triggering of a solar flare might be related with the plasma instability caused by the surplus longitudinal electric currents at some local regions in the solar atmosphere.     

太阳耀斑区磁场和电流研究的一些新进展

在太阳耀斑区磁场和电流研究方面，文中将着重介绍太阳横向磁场方位的确定，太阳活动区磁场的非热性表示、太阳耀斑前后的活动区磁场变化、以及耀斑核块与活动区纵向电流密度极大点位置的关系等几个重要问题的研究现状。     

Particle acceleration in reconnecting current sheets

We study motions of charged particles in reconnecting current sheets (CS) which have both transverse (perpendicular to the current sheet plane) and longitudinal (parallel to the electric current inside the sheet) components of the magnetic field. Such CS, called non-neutral, are formed in regions of magnetic field line reconnection in the solar atmosphere. We develop an analytical technique which allows us to reproduce previous results concerning the influence of transverse fields on particle motion and acceleration. This technique also allows us to evaluate the effect of the longitudinal field. The latter increases considerably the efficiency of particle acceleration in CS. The energizing of electrons during the main phase of solar flares can be interpreted as their acceleration in non-neutral CS.     

Magnetic Helicity Injection in Solar Active Regions

We present the evolution of magnetic field and its relationship with mag- netic(current)helicity in solar active regions from a series of photospheric vector magnetograms obtained by Huairou Solar Observing Station,longitudinal magne- tograms by MDI of SOHO and white light images of TRACE.The photospheric current helicity density is a quantity reflecting the local twisted magnetic field and is related to the remaining magnetic helicity in the photosphere,even if the mean current helicity density brings the general chiral property in a layer of solar active regions.As new magnetic flux emerges in active regions,changes of photospheric cur- rent helicity density with the injection of magnetic helicity into the corona from the subatmosphere can be detected,including changes in sign caused by the injection of magnetic helicity of opposite sign.Because the injection rate of magnetic helicity and photospheric current helicity density have different means in the solar atmosphere, the injected magnetic helicity is probably not proportional to the current helicity den- sity remaining in the photosphere.The evidence is that rotation of sunspots does not synchronize exactly with the twist of photospheric transverse magnetic field in some active regions(such as,delta active regions).They represent different aspects of mag- netic chirality.A combined analysis of the observational magnetic helicity parameters actually provides a relative complete picture of magnetic helicity and its transfer in the solar atmosphere.     

An Automatic Detection for Solar Active Regions Based on Scale-Invariant Feature Transform and Clustering by Fast Search and Find of Density Peaks

The solar active regions are the regions where various active phenomena occur in the solar atmosphere. Accurate detection and identification of the solar active regions are of great scientific significance to understand the formation mechanism of the solar magnetic field. In this paper, we propose an automatic detection and recognition technology for solar active regions based on the advantages of Scale Invariant Feature Transform (SIFT) and Clustering by Fast Search and Find of Density Peaks (DPC). Firstly, enhance the contrast of longitudinal magnetic image of Helioseismic and Magnetic Imager (HMI) of Solar Dynamics Observatory (SDO). Then extract the feature points by SIFT. Finally, cluster the feature points by fast search and find of density peaks so as to automatically detect and identify the solar active regions. The results show that the combination of SIFT and DPC can accurately detect the solar active region without human-computer interaction.     

太阳活动区水平电流的估算

在非线性无力场的模型之下,我们设计出了一个估计太阳活动区水平电流的计算方法。解析解的检验表明,该方法是收敛的。这一方法避免了以前外推方法中沿中性线所出现的奇异性     

On the magnetic reconnection of electric currents in solar flares

The role of the electric currents distributed over the volume of an active region on the Sun is considered from the standpoint of solar flare physics. We suggest including the electric currents in a topological model of the magnetic field in an active region. Typical values of the mutual inductance and the interaction energy of the coronal electric currents flowing along magnetic loops have been estimated for the M7/1N flare on April 27, 2006. We show that if these currents actually make a significant contribution to the flare energetics, then they must manifest themselves in the photosphericmagnetic fields. Depending on their orientation, the distributed currents can both help and hinder reconnection in the current layer at the separator during the flare. Asymmetric reconnection of the currents is accompanied by their interruption and an inductive change in energy. The reconnection of currents in flares differs significantly from the ordinary coalescence instability of magnetic islands in current layers. Highly accurate measurements of the magnetic fields in active regions are needed for a quantitative analysis of the role of distributed currents in solar flares.     

Vertical current and a 3B/X12 flare in a highly sheared active region (NOAA 6659) on June 9, 1991

NOAA active region 6659, during its June 1991 transit across the solar disk, showed highly sheared vector magnetic field structures and produced numerous powerful flares, including five white-light flares. Photospheric vector magnetograms of this active region were obtained at the Huairou Solar Observing Station of the Beijing Astronomical Observatory. After the resolution of the 180° ambiguity of the transverse magnetic field and transformation of off-center vector magnetograms to the heliographic plane, we have determined the photospheric vertical current density and discussed the relationship with powerful flares. The following results were obtained: (a) The powerful 3B/X12 flare on June 9, 1991 was triggered by the interaction between the large-scale electric current system and magnetic flux of opposite polarity. (b) The kernels of the powerful Hβ flare (sites of the white-light flare) were close to the peaks of the vertical electric current density. (c) Some small-scale structures of the vertical current relative to the magnetic islands of opposite polarity have not been found. This probably implies that the electric current is not always parallel to the magnetic field in solar active regions.     

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.