STEREO卫星的CME观测研究进展

简要回顾利用"日地关系天文台"(Solar Terrestrial Relations Observatory,STEREO)卫星的立体观测资料在日冕物质抛射(Coronal Mass Ejection,CME)研究方面已取得的一些重要进展,主要包括(1)通过极紫外成像仪观测到的日冕极紫外暗化来更准确地估计CME质量,研究CME演化的结构特征;(2)利用STEREO卫星日冕仪的双角度观测,在CME立体传播特征方面取得的新进展;(3)STEREO卫星日球成像仪具有广阔的视场范围,可以跟踪研究CME从太阳表面爆发到形成行星际日冕物质抛射(Interplanetary CME,ICME),及其在内日球层和近地空间的演化特征以及运动特征等。同时,也介绍了利用三角测量技术测定CME特征物理量的新方法。     

太阳的空间观测与研究Ⅱ—太阳高能粒子和等离子体云的抛射

太阳空间观测揭示出太阳的高能电子,高能质子发射以及γ射线爆发。证实了有关的太阳射电辐射理论,揭示出太阳耀斑中的核反应。日冕物质抛射和耀斑等离子体云的空间观测揭示出它们之间的区别和联系,认识到耀斑的热区和冷区。在阳和日球磁场以观测发展了磁流体动力学理论。     

卫星黑子衰减触发的喷流事件

详细分析了一次太阳低层大气磁场重联触发的喷流事件.这次喷流发生在2014年8月1日,爆发自美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration, NOAA)活动区12127边缘的一个卫星黑子处.该喷流爆发包括日浪、紫外喷流、极紫外高温和低温喷流.大熊湖太阳天文台(Big Bear Solar Observatory,BBSO)的Goode Solar Telescope (GST)高分辨率氧化钛(TiO)谱线的光球观测显示,喷流爆发过程中,卫星黑子一直衰减.到喷流结束,卫星黑子面积共减少了80%.在此过程中,太阳动力学天文台(Solar Dynamics Observatory, SDO)日球磁场成像仪(Helioseismic and Magnetic Imager, HMI)的视向磁场观测表明,该卫星黑子对应的负极磁场与相邻的正极磁场发生明显对消,产生喷流足部亮点.根据SDO卫星太阳大气成像仪(Atmospheric Imaging Assembly, AIA)的多波段观测,该足部亮点首先出现在紫外1600?波段.待紫外(1600?)喷流从紫外足部亮点顶部向上喷发,在极紫外波段也观测到相应的亮源.随着足点源亮度突然增强,有明显的极紫外低温喷流和日浪从足部亮点侧面喷发.从GST的高分辨率Hα图像上,可见日浪由许多精细纤维组成,这些纤维扎根在足点源的东南侧.根据从光球层过色球层再到日冕层的多波段高分辨率观测,色球中下层的磁场对消触发了这次喷流事件.向上喷发的物质流可以携带能量进入上层大气,并加热上层大气.研究结果表明,低层大气磁重联可能对解决日冕加热问题起重要作用.     

日冕物质抛射及其驱动激波的多波段和多视角研究

<正>日冕物质抛射(Coronal Mass Ejection, CME)是太阳大气中剧烈的爆发现象之一.其爆发通常能释放大量的能量并抛射大量磁化等离子体. CME所驱动的激波能进一步导致太阳高能粒子事件(Solar Energetic Particle,SEP)的发生,并可能影响航天器和宇航员的安全.因此,研究CME及其驱动激波的形成机制和性质有利于我们更加清晰地了解及监测它们的运动过程,     

太阳爆发探测小卫星高能暴谱仪

太阳爆发探测小卫星(Small Explorer for Solar Eruptions,简称SMESE)是中国法国合作小卫星.SMESE计划在下一个太阳活动峰年(-2011年)发射上天,同时观测太阳上两类最剧烈爆发现象:耀斑和日冕物质抛射(CME),瞄准当代科学的前沿课题,同时兼顾空间天气学的应用需要.高能暴谱仪(High Energy Burst Spectrometer,简称HEBS)是太阳爆发探测小卫星上3大主要载荷之一,采用世界最新高能量分辨LaBr3闪烁探测器,观测太阳10 keV-600 MeV的高能辐射.其能量分辨优于3.0%@662 keV,高于目前通用闪烁探测器的2倍以上,可望在耀斑和CMEs的能量释放,粒子加速,以及耀斑和CMEs之间的关系研究方面取得突破.     

超强太阳质子事件及相伴现象特征分析

依据卫星和地面的观测数据,分析了峰值流量达到或超过10 000 pfu(1 pfu=1proton.cm~2.s~(-1).sr~(-1))的超强太阳质子事件相伴的太阳耀斑、曰冕物质抛射(CME)驱动激波的曰地传播速度、源区的曰面经度、卡林顿经度以及相伴的磁暴等现象.研究表明,超强太阳质子事件源区的曰面经度范围为E30°Longitude≤W75°.超强太阳质子事件源区分布在2个卡林顿经度带,分别为130°~220°的区域和260°~320°的区域.超强太阳质子事件都伴随着强烈的太阳耀斑和快速CME,CME驱动的激波从太阳到地球的平均速度超过1200 km/s.除一个超强太阳质子事件相伴的磁暴略低于强磁暴外,其余8个都伴有Dst≤-100 nT的强烈磁暴.     

基于空时显著性的日冕物质抛射检测

日冕物质抛射(Coronal Mass Ejection, CME)是一种剧烈的太阳爆发现象, 它会对行星际空间造成严重扰动, 进而影响人类生产、生活. 基于CME的时空显著性, 将显著性检测方法引入到CME检测中, 利用结构化矩阵分解SOHO (Solar and Heliospheric Observatory)的大角度光谱日冕仪(Large Angle and Spectrometric Coronagraph Experiment, LASCO) C2的日冕图像对应的特征矩阵, 从中恢复出稀疏部分获得显著前景. 然后考虑CME运动时产生的时间显著性, 从而去除非CME结构(如冕流), 得到最终检测结果. 实验表明, 以人工目录协调数据分析中心(Coordinated Data Analysis Workshop, CDAW)检测结果为基准时, 所提方法不仅在检测CME数量上比计算机辅助跟踪软件包(Computer Aided CME Tracking Software package, CACTus)和太阳爆发事件检测系统(Solar Eruptive Event Detection System, SEEDS)有优势, 还在CME中心角度和张角宽度等特征物理参数测量上比CACTus和SEEDS更接近CDAW目录参考值.     

基于机器学习的日冕仪图像分类方法研究

日冕物质抛射(Coronal Mass Ejection, CME)的检测是建立CME事件库和实现对CME在行星际传播的预报的重要前提. 通过Visual Geometry Group (VGG) 16卷积神经网络方法对日冕仪图像进行自动分类. 基于大角度光谱日冕仪(Large Angle and Spectrometric Coronagraph Experiment, LASCO) C2的白光日冕仪图像, 根据是否观测到CME对图像进行标记. 将标记分类的数据集用于VGG模型的训练, 该模型在测试集分类的准确率达到92.5%. 根据检测得到的标签结果, 结合时空连续性规则, 消除了误判区域, 有效分类出CME图像序列. 与Coordinated Data Analysis Workshops (CDAW)人工事件库比较, 分类出的CME图像序列能够较完整地包含CME事件, 且对弱CME结构有较高的检测灵敏度. 未来先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)卫星的莱曼阿尔法太阳望远镜将搭载有白光日冕仪(Solar Corona Imager, SCI), 使用此分类方法将该仪器产生的日冕图像按有无CME分类. 含CME标签的图像将推送给中国的各空间天气预报中心, 对CME进行预警.     

基于支持向量机的太阳磁场活动区极性反转线位置的探测

太阳磁场的极性反转线(Polarity Inversion Line, PIL)是研究太阳活动、分析太阳磁场结构演变和预测太阳耀斑最重要的日面特征之一.磁场极性反转的位置是太阳耀斑和暗条可能出现的位置."先进天基太阳天文台(ASO-S)"是中国首颗空间太阳专用观测卫星,其搭载的"全日面矢量磁像仪(Full-Disk Vector Magnetograph, FMG)"主要任务是探测高空间、高时间分辨率的全日面矢量磁场.为了提高观测数据使用效率、快速监测太阳活动水平、提高太阳耀斑与日冕物质抛射的预报水平以及更好地服务于FMG数据处理与分析系统,采用了图像自动识别与处理技术,更加精确有效地检测极性反转线.从支持向量机(Support Vector Machine, SVM)的模型出发,将极性反转线位置的探测问题转化为一个模式识别中的二分类问题,提出了一种基于支持向量机的极性反转线检测算法,自动探测与识别太阳动力学天文台(Solar Dynamics Observatory, SDO)日震和磁成像仪(Helioseismic and Magnetic Imager, HMI)磁图的极性反转线位置.与现有算法的对比结果表明,此算法可以精确直观地检测太阳活动区的极性反转线.     

太阳的空间观测与研究Ⅱ—太阳高能粒子和等离子体云的抛射

太阳空间观测揭示出太阳的高能电子、高能质子发射以及γ射线爆发。证实了有关的太阳射电辐射理论、揭示出太阳耀斑中的核反应。日冕物质抛射和耀斑等离子体云的空间观测揭示出它们之间的区别和联系, 认识到耀斑的热区和冷区。太阳和日球磁场观测发展了磁流体动力学理论     

局部对流和非局部对流太阳模型的绝热振动频率

研究和比较了熊大闰的非局部对流和局部对流太阳包层模型的本征振动频率,观测与理论振动频率之间的差别小于1％．它们分为两个分立的群:对l≥60的模,其观测与理论本征振动频率的差完全分布在一条狭窄的倾斜带状区域之内,这说明理论太阳对流区模型大致反映了太阳在r=(0．70-0．95)R⊙这一区域的真实结构,理论与观测频率误差来自外层区域;对于l<60的模,理论的振动频率要比观测的振动频率小,这意味着在对流不稳定区上部的区域温度偏低．另一方面局部对流包层模型的频率差比非局部对流包层模型的频率差更为弥散,中低频端(v<3000)两者差别不大;而在高频端(v≥3000)局部对流包层模型的频率比非局部的频率要高,这意味着局部对流模型在对流区之下的辐射区的温度比非局部对流模型温度要高,非局部对流模型比局部对流模型更接近观测．     

The non-uniform pattern in full-disc vector magnetograms and its correction

The Solar Magnetism and Activity Telescope (SMAT) has been operational at Huairou Solar Observing Station since the end of 2005. Its scientific projects are the observational study of full-disc vector magnetic field and Hα chromospheric activities. In this paper, the Fourier low-frequency passing filter and the large-scale polynomials fit methods have been employed to analyse and remove the non-uniform pattern (NUP) in the full-disc Stokes V image. These methods are useful to effectively improve the quality of SMAT's data. The following main results have been obtained. (1) An intrinsic large-scale spatial distribution of NUP appears in SMAT's full-disc Stokes V image and its average amplitude accounts for 2 per cent of sunspots' field of kG. (2) NUP is testified as instrumental polarization through data reduction and observational explanation (passband shift). There are pseudo-passband shift in the wide field of view of SMAT due to NUP, and the maximum shifting value from the solar disc centre to the solar disc limb is 0.12 Å. (3) As an example, after removing SMAT's NUP in the Stokes V image, the correlation coefficients of the magnetograms become 78 per cent between SMAT and MDI (Michelson Doppler Imager project) on the SOHO ( Solar and Heliospheric Observatory ) satellite, and 92 per cent between SMAT and the SMFT (Solar Magnetic Field Telescope) at Huairou.     

Two Sympathetic Homologous CMEs on 2002 May 22

Sympathetic coronal mass ejections (CMEs) usually occur in different active regions connected by interconnecting magnetic loops, while homologous CMEs occur within the same active region with an almost the same background magnetic field, and so are similar in shapes. Two sympathetic CMEs erupted within 3 hours on 2002 May 22, originating from the same active region, AR 9948. Their multi-wavelength data were collected and analyzed. It is suggested that emerging flux triggered the occurrence of the first CME and the corresponding flare, the reconnection inflow of which in turn triggered the eruption of the second CME. Based on the fact that the two sympathetic CMEs have many similarities, in their shapes, their low-lying dimming areas, etc., we tentatively propose, for the first time, the phenomenon of sympathetic homologous CMEs.     

An Observational Study on Coronal Hard X-ray Sources in Flares

Observational studies on solar ?ares with footpoints partially occulted by the solar limb provide an important method for diagnostics of coronal hard X-ray emissions. The statistics of hard X-ray sources in 71 such ?ares observed by RHESSI (Reuven Ramaty High-Energy Solar Spectroscopic Imager) show that the two kinds of hard X-ray sources proposed in previous studies (i.e., the sources with respectively a smaller and larger spatial separations between the thermal and non-thermal sources of coronal hard X-ray emissions) have no evident difference in the aspects of their photon spectra, images, light curves, GOES durations, etc. The area of the radiation region, the ?are's total thermal energy and GOES duration are well correlated with the distance of separation. These results support some uni?ed models of solar ?ares proposed in recent years, and indicate that the Masuda ?are is only a kind of special event, which does not possess the general features of coronal hard X-ray emissions     

耀斑日冕硬X射线源观测研究

对于足点被日面边缘遮挡住的耀斑的观测研究是诊断日冕硬X射线辐射的一个重要方法.通过统计分析RHESSI (Reuven Ramaty High-Energy Solar Spectroscopic Imager)卫星观测到的71个此类耀斑硬X射线源发现,前人提出的两类源,即日冕X射线辐射中热辐射与非热辐射源区空间分离较小的源和分离较大的源,在能谱、成像、光变曲线以及GOES持续时间等方面都没有显著的区别,其中辐射区的面积、耀斑总热能以及GOES持续时间与分离距离之间有很好的相关性.这些结果支持近年来提出的一些耀斑统一模型.同时也表明Masuda耀斑只是一类非常特殊的事件,不具有日冕硬X射线辐射的一般特征.     

Features of the Solar Active Cycles

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｏｌａｒａｃｔｉｖｅｃｙｃｌｅｉｓｕｓｕａｌｌｙｄｅｓｃｒｉｂｅｄｗｉｔｈｔｈｅｒｅｌａｔｉｖｅｓｕｎｓｐｏｔｎｕｍｂｅｒｓ.Ａｎａｌｙｓｅｓｏｆｈｉｓ ｔｏｒｉｃａｌｄａｔａｏｎｔｈｅｒｅｌａｔｉｖｅｓｕｎｓｐｏｔｎｕｍｂｅｒｓｈａｖｅｒｅｖｅａｌｅｄａｗｅａｌｔｈｏｆｉｎｆｏｒｍａｔｉｏｎａｂｏｕｔｔｈｅｓｏｌａｒａｃｔｉｖｅｃｙｃｌｅ (ＨｏｎｇＱｉｎｆａｎｇ 1 990 ,1 994;ＺｈｏｎｇＳｈｕｈｕａ 1 991 ,1 995 ) .Ｔｈｅｓｏ ｃａｌｌｅｄ 1 1 ｙｅａｒｐｅ ｒｉｏ…     

Analysis of the Properties of Super Solar Proton Events and Associated Phenomena

The solar flares, the speeds of shocks propagated in the solar-terrestrial space and driven by coronal mass ejections (CMEs), the heliographic longitudes and Carrington longitudes of source regions, and the geomagnetic storms, which are accompanied by the super solar proton events with a peak ?ux equal to or exceeding 10 000 pfu, have been studied by using the data of ground-based and space observations. The results show that the heliographic longitudes of source regions of super solar proton events distributed in the range from E30? to W75°. The Carrington longitudes of source regions of super solar proton events distributed in the two longitudinal belts, 130°∼220° and 260°∼320°, respectively. All super solar proton events were accompanied by major solar flares and fast CMEs. The averaged speeds of shocks propagated from the sun to the Earth were greater than 1 200 km/s. Eight super solar proton events were followed by major geomagnetic storms (Dst≤−100 nT), except that one super solar proton event was followed by a geomagnetic storm with the geomagnetic activity index Dst=−96 nT, a little smaller than that of major geomagnetic storms.     

太阳总辐照的演化特征分析

太阳总辐照在23和24太阳活动周的显著周期分别为35 d和26 d,进而推断太阳的准旋转周期在23和24太阳活动周也分别为35 d和26 d.太阳总辐照在24周极小期的值可能与蒙德极小期的值相近.在一个太阳旋转周到几个月的时间尺度上,太阳黑子是引起太阳总辐照变化的主要原因,但不是唯一的原因;在几天到一个太阳旋转周的时间尺度上,太阳总辐照的变化与MgⅡ特征指数是不相关的.     

A Study of the Periodic Variations of Solar Magnetic Fields During Maxima and Minima of Solar Activity

By using the solar magnetic ?eld data of Wilcox Observatory from 1975 to 2010, the short-time periodicities of solar mean magnetic ?elds during solar maximum and minimum years are analyzed. The results reveal that the solar magnetic ?elds mainly exhibit the approximate periods of 9 d, 13 d, and 27 d. During maximal solar activity the period about 27 d is most conspicuous, while during minimal solar activity the most evident period is approximately 13.5 d (except the solar minimum in the years 1984-1986). These results imply that solar active regions exhibit evidently different distributions in the periods of maxima and minima of solar activity.     

A Statistical Analysis of the Type-III Bursts in Centimeter and Decimeter Wavebands

A statistical analysis of the type-III bursts observed by the spectrographs in the ranges of 625∼1500 MHz, 2600-3800 MHz, and 5200-7600 MHz during the 23rd solar cycle (from 2000 July to 2004 September) is carried out. The distribution of the type-III bursts, and their durations, frequency drift rates, polarization degrees and frequency bandwidths are given in this paper. The results indicate that the average values of the frequency drift rates and frequency bandwidths increase with the frequency. The average values of the durations and polarization degrees are neither constant nor uniformly varied over a broad frequency range. Most of type-III bursts are distributed in the range from 625 to 3800 MHz, and decrease with the frequency in number. This analysis shows that the places of electron acceleration and energy release are mainly in the decimetric range, and the characteristic of this frequency range is possibly related with the magnetic configuration at the decimeter wavelengths, as well as the electron acceleration in the magnetic reconnection site close to the main flare. However, there are also a considerable number of type-III bursts in the range of 5200-7600 MHz, it means that the sites of electron acceleration are widely distributed in the coronal region. The radiation mechanisms of type-III bursts at the centimeter-decimeter wavelengths include most probably the coherent plasma radiation and the emission process of electron cyclotron maser.