日蚀观测太阳微波射电源的磁拱结构

1980年2月16日云南日全蚀期间,在月掩具有双极黑子群的活动区过程中,分别由2,3.2,8.2和21厘米波段的蚀变斜率曲线峰值时刻,定出各波段射电源核心沿掩蚀方向的部位,将其一一移至相应有效辐射层的高度上,用几簇封闭的弧线连结起来,得到射电源的磁拱结构.分析了射电源的位置、角径、流量和空间分布同磁场的强度、范围、立体角和形状之间的对应关系.其中8.2厘米的结果同甚大阵观测的太阳6厘米环状结构基本一致.有效辐射层与磁拱相交的区域,主要产生磁回旋辐射,形成射电源的“核”;有效辐射层以上受磁拱约束的光学深度薄的区域,主要产生热轫致辐射,形成射电源的“晕”.由于有效辐射层随波长增大而升高,磁拱中对较长波长为核的区域,可能就是较短波长晕的组成部分.     

1968年9月22日日食3厘米波段强度观测

介绍参加1968年9月22日日食观测的两架3厘米波段总强度射电望远镜与观测概况,观测资料的处理和缓变射电源的证认.给出日食期间日面上黑子、谱班和日冕凝聚区相应的缓变射电源的几个参数:角径(月心运动方向上)、流量密度、平均亮温度与高度.     

1968年9月22日日食的3.2厘米波段圆偏振观测

本文叙述了紫金山天文台在1968年9月22日进行的日食观测中3.2厘米波段圆偏振观测的概况及计算、分析的结果。我们的观测得到日面各射电源的圆偏振流量密度、一维角径、非常波和寻常波的亮温度之差、磁场、偏振度、高度等参数(见总表)以及下列结果:1.不仅黑子,而且小亮点和谱斑都有明显的圆偏振效应。后两者的偏振流量密度和中、小黑子的偏振流量密度在同一范围。2.利用了日食观测的高分辨特性,观测到332号黑子与其上空的偏振源有一一对应的核——半影结构。并分解了该偏振源的双核结构,得到最小细节是2.″5角距离的核间半影。3.观测现象表明,偏振源从日面后转出时偏振波的旋转方向发生反转。     

1968年9月22日日食射电观测

本文综合分析了1968年9月22日新疆日全食3.2、11.1和21厘米波长的射电观测资料,得出了射电源的流量和活动区活动性的关系、射电源辐射与谱斑及黑子的相关等观测结果。另外,从综合三个波段的资料通盘考虑了射电源流量值的误差分析、射电源的角径和高度、射电食甚、射电太阳等效半径和日面小爆发等。     

黑子周围光球亮点的特征提取与比较

光球亮点是位于米粒暗径中的小尺度发亮结构,普遍认为它是千高斯磁流管的足点.采用云南澄江抚仙湖1 m新真空太阳望远镜(New Vacuum Solar Telescope,NVST)在Ti O波段的NOAA 11598观测数据,研究黑子周围光球亮点的特性变化.首先识别黑子,通过形态学膨胀技术把黑子外围划分为4个环形区域,然后采用一个结合了拉普拉斯与形态学技术的自动算法识别亮点,并在三维时空立方体中跟踪亮点的演化,最后研究了4个环形区域中亮点的特性变化,包括密度、强度、面积、形状和速度.统计结果和假设检验均表明位于黑子外围不同区域的光球亮点的密度、等效直径和速度明显受黑子强磁场的影响,其峰值不在最靠近黑子的区域,而是位于第2个区域,并随着远离黑子,其密度减小,直径减小而速度增加;最大强度比总体呈现出逐渐减小的趋势;而形状基本没有变化,与所处的区域无关.     

恒星黑子的观测

本文对恒星黑子的观测方法和结果作了综合评述。介绍了恒星黑子温度的多色测光测定方法；黑子大小，温度和分布情况的测光畸变波黑子模型解，和高信噪比谱线轮廓多普勒成像方法；以及黑子寿命观测统计方法等的基本原理和研究进展。对已取得的有关恒星黑子的观测分析结果作了概括，与太阳典型黑子情况作了对比，并对恒星黑子的巨黑子，极区黑子以及长寿命黑子特殊性作了讨论，对需要进一步观测研究的问题作了总结。     

1972年8月太阳活动区的形态研究 Ⅰ.黑子精细结构的形态

云南天文台成功地拍到了1972年8月太阳大黑子群的自光精细结构照片.从该黑子群形态的逐日演变得出如下结论:1.观测到了与黑子本影旋转运动有关的黑子动力学形态,即半影纤维排列的旋涡结构.2.该黑子群中部本影的旋转、自行和分裂运动,以及它东面蛇形半影长纤维的被拉长、弯曲和蜕化是本活动区光球形态变化的主要特征.这些运动是属于该黑子群内部固有的特性,似乎与较差自转等原因无直接联系.3.光球黑子形态变化的激发过程和色球耀斑活动的强烈程度对应很好,显示出两者之间可能存在比较密切的物理联系.     

1980年11月第569号黑子群和耀斑的形态研究

本文对云台编号569黑子群(Boulder2776)80、11、1—80、11、13的黑子、磁中性线、耀斑、x射线、射电爆发等活动现象进行了描述和统计,结果表明该活动区老黑子群纵场中性线西侧新浮磁通量的发展,它的S极性区域向西老场N极区不断扩展,对该活动区一系列相似耀斑的爆发有着直接影响,并且当这些掩盖新浮磁通量的S极性黑子时对应x事件的比率增大。     

日面新生黑子的经度分布

以云南天文台对５２２个太阳自转周的观测资料统计,在可见日面上新生的黑子,各个太阳活动周出现频数不等。从中筛选出面积ＣＹ≥５００的２２８群,以及ＣＹ≥１２００的２９群,它们分别都在经度上呈相对集中性,但又多随时间变化而漂移,在时间分布上无规律性。在可比的太阳第２１和２２活动周内,新生黑子对应的最强烈活动区只有８１２００和９２３９０,另外是８２４９５回转的８２５３３对应在最强烈活区,说明新生大黑子无固定的活动源。     

1989年7月5日耀斑活动区的磁场特征

本文详细分析了1989年7月5日有连续发射的耀斑对应的活动区磁场。得出:磁场强度和黑子面积分布都有“前导大后随小”的特征;两异极黑子挤压位置的中性线呈“V”形;产生连续发射的四个耀斑核,除一个位于宁静背景上外,其余三个均位于中性线两侧;连续发射最明显的B点耀斑核位于磁剪切和磁挤压的交点以及磁场梯度最大(0.52高斯公里~(-1))的位置上。     

Determining the Solar Source of a Magnetic Cloud Using a Velocity Difference Technique

For large eruptions on the Sun, it is often a problem that the core dimming region cannot be observed due to the bright emission from the flare itself. However, spectroscopic data can provide the missing information through the measurement of Doppler velocities. In this paper we analyse the well-studied flare and coronal mass ejection that erupted on the Sun on 13 December 2006 and reached the Earth on 14 December 2006. In this example, although the imaging data were saturated at the flare site itself, by using velocity measurements we could extract information on the core dimming region, as well as on remote dimmings. The purpose of this paper is to determine more accurately the magnetic flux of the solar source region, potentially involved in the ejection, through a new technique. The results of its application are compared to the flux in the magnetic cloud observed at 1 AU, as a way to check the reliability of this technique. We analysed data from the Hinode EUV Imaging Spectrometer to estimate the Doppler velocity in the active region and its surroundings before and after the event. This allowed us to determine a Doppler velocity ‘difference’ image. We used the velocity difference image overlayed on a Michelson Doppler Imager magnetogram to identify the regions in which the blue shifts were more prominent after the event; the magnetic flux in these regions was used as a proxy for the ejected flux and compared to the magnetic cloud flux. This new method provides a more accurate flux determination in the solar source region.     

Analysis and interpretation of soft X-ray photographs of coronal active regions taken with Fresnel zone plates

Soft X-ray photographs of the Sun taken at O vii 21.6 Å and in a spectral band ranging from 13.2 to 22.1 Å have been analysed in order to establish spatially resolved maps of temperature and emission measure for several active regions in the corona. The photographs were taken on 11 March, 1971, and on 2 March, 1972, with Fresnel zone plate cameras which were flown on ESRO and NRL sounding rockets.In Part I of this paper we first deal with those aspects of the instrumentation which are important for setting up a suitable image analysis procedure. We discuss the characteristics of the wavelength dependent image formation by zone plates combined with absorption filters. Results of the calibration of the X-ray film are given. Then we describe a specific iterative data reduction procedure and finally present the resulting maps of temperature and emission measure for a selected active region. In Part II corresponding results for further active regions will be given and discussed.     

Electron temperature and emission measure variations during solar X-ray flares

X-ray emission from seventeen X-ray flares was analyzed to obtain electron temperatures and emission measures associated with the source region in the solar corona. The source region was assumed to be isothermal with a Maxwellian electron velocity distribution.Flares which were characterized by a rapid initial X-ray flux increase were found to also have a rapid initial rise in electron temperature and emission measure. Flares which were characterized by a gradual initial X-ray energy flux increase were found to have a less rapid initial rise in electron temperature and emission measure. In all X-ray flares studied the peak temperature chronologically preceded the peak X-ray flux and the peak flux never came after the peak emission measure.Based on a dissertation submitted to The Catholic University of America, Washington, D.C.     

Australia Telescope Compact Array 1.2-cm observations of the massive star-forming region G305.2+0.2

We report on Australia Telescope Compact Array observations of the massive star-forming region G305.2+0.2 at 1.2 cm. We detected emission in five molecules towards G305A, confirming its hot core nature. We determined a rotational temperature of 26 K for methanol. A non-local thermodynamic equilibrium excitation calculation suggests a kinematic temperature of the order of 200 K. A time-dependent chemical model is also used to model the gas-phase chemistry of the hot core associated with G305A. A comparison with the observations suggest an age of between  2 × 10⁴  and  1.5 × 10⁵ yr  . We also report on a feature to the south-east of G305A which may show weak Class I methanol maser emission in the line at 24.933 GHz. The more evolved source G305B does not show emission in any of the line tracers, but strong Class I methanol maser emission at 24.933 GHz is found 3 arcsec to the east. Radio continuum emission at 18.496 GHz is detected towards two H  ii regions. The implications of the non-detection of radio continuum emission towards G305A and G305B are also discussed.     

On the Microwave Spike Emission of the September 6, 1992 Flare

The main aim of this paper is to estimate, from multispectral observations, the plasma parameters in a microwave burst source which was also the site of spike emission. This information is essential for the determination of the spike emission process. By analyzing one-dimensional source distributions observed with the SSRT at 5.7 GHz and correlating them with Yohkoh X-ray and Nobeyama 17 GHz images, we have concluded that the microwave emitting region was larger than the soft X-ray loop-top source, and that the origin of the burst could be explained by gyrosynchrotron emission of non-thermal electrons in a magnetic field of approximately 100 G. It has been shown that the source of 5.7 GHz spikes observed during the burst was located close to an SXR-emitting loop with high density and temperature and a relatively low magnetic field. Thus, plasma emission is the most favourable radiation mechanism for the generation of the sub-arc-second microwave pulses.     

A two-component model of impulsive microwave burst emission consistent with soft and hard X-rays

A two-component (core-halo) emission model has been applied reconciling hard and soft X-ray burst emissions with the microwave burst radiation. The core region is represented by a nonthermal energy distribution (Maxwellian+power law tail) and assumed to be surrounded by a thermal halo. Parameters characterizing the energy distribution and emission measures have been derived numerically from soft and hard X-ray measurements. Using an artificial magnetic field model the microwave flux spectrum has been calculated on the basis of gyro-synchrotron emission and absorption by solving the equation of radiation transfer along the ray trajectories. Open parameters were used to adapt the spectrum to the radio measurements.Thus probable informations about the most appropriate magnetic field parameters as well as about the time- and frequency- dependent source diameters (yielding growth velocities of the core region during the impulsive phase) are deduced for the burst of 1972 May 18 as an example. A fit of the observed spectrum at the burst maximum is consistent with a magnetic field of 150O G at the core centre decreasing up to about 40 G at the top of the halo at a height of 50 000 km above the centre, a core density of 10¹⁰ cm^–3 decreasing to 10⁹ cm^–3 at the outer halo boundary, and a core diameter of 15 000 km (]20).Due to the simple geometry and emission process adopted,- the model refers primarily to special impulsive bursts. For the representation of broad band microwave bursts, e.g. type IV , events, a more complex source geometry and/or other variants of the emission mechanism must be invoked.     

Radio Pulsar Death Line Revisited: Is PSR J2144-3933 Anomalous?

We present Chandra X-ray observations of the Hydra A cluster of galaxies, and we report the discovery of structure in the central 80 kpc of the cluster's X-ray-emitting gas. The most remarkable structures are depressions in the X-ray surface brightness, approximately 25-35 kpc in diameter, that are coincident with Hydra A's radio lobes. The depressions are nearly devoid of X-ray-emitting gas, and there is no evidence for shock-heated gas surrounding the radio lobes. We suggest that the gas within the surface brightness depressions was displaced as the radio lobes expanded subsonically, leaving cavities in the hot atmosphere. The gas temperature declines from 4 keV at 70 kpc to 3 keV in the inner 20 kpc of the brightest cluster galaxy (BCG), and the cooling time of the gas is approximately 600 Myr in the inner 10 kpc. These properties are consistent with the presence of an approximately 34 M middle dot in circle yr-1 cooling flow within a 70 kpc radius. Bright X-ray emission is present in the BCG surrounding a recently accreted disk of nebular emission and young stars. The star formation rate is commensurate with the cooling rate of the hot gas within the volume of the disk, although the sink for the material that may be cooling at larger radii remains elusive. A bright, unresolved X-ray source is present in the BCG's nucleus, coincident with the radio core. Its X-ray spectrum is consistent with a power law absorbed by a foreground NH approximately 4x1022 cm-2 column of hydrogen. This column is roughly consistent with the hydrogen column seen in absorption toward the less, similar24 pc diameter VLBA radio source. Apart from the point source, no evidence for excess X-ray absorption above the Galactic column is found.     

S5 2007+777的射电性质研究

S5 2007+777是一个典型的低峰值频率的蝎虎天体,该天体具有kpc尺度的X射线喷流,文献中利用模型估算的方法,得出X射线波段的多普勒因子达到13.0,从而喷流尺度可以达到Mpc量级.在此,搜集了有关S5 2007+777的欧洲甚长基线射电干涉网(European VLBI Network, EVN)高分辨率档案数据、美国甚长基线射电干涉网(Very Long Baseline Array, VLBA) 15 GHz观测数据等,研究了喷流的射电结构、亮温度、自行等方面的性质,发现该源的甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)不同波段的喷流方向一致,但与文献中给出的kpc尺度的X射线喷流和甚大阵(Very Large Array, VLA)射电喷流方向存在一定的差异,说明该源的喷流辐射存在多普勒增亮效应.由VLBI观测得到的亮温度,估算了该源的射电多普勒因子的平均值及中值均为5.0,此值小于文献中X射线波段的多普勒因子,但与文献中利用其他方法得到的射电波段多普勒因子是一致的;另外,对多历元观测数据的拟合发现此源相同波段的各个成分在长历元上没有明显的自行,短历元上的自行甚至是视超光速运动.这可能是由低表面亮度成分中心位置的转移造成的.这同时也验证了之前估算的射电多普勒因子不是很大,小于X射线波段多普勒因子的结论.利用所得到的射电多普勒因子,发现该源具有较大尺度的本征射电喷流,可达到0.5 Mpc,由于这里使用的是均值,因此说明该源也有可能具有接近巨射电星系尺度的喷流.     

Microwave,ultraviolet, and soft X-Ray observations of hale region 16898

Hale region 16898 was observed by the Westerbork Synthesis Radio Telescope at 6 cm and by the Ultraviolet Spectrometer and Polarimeter and the X-Ray Spectrometer on the Solar Maximum Mission satellite. Optical pictures of the same active region were taken at Sacramento Peak, Big Bear, and Meudon Observatories. The radio emission mechanisms are identified by comparing radio data with ultraviolet and soft X-ray data. The height of the radio sources and the magnetic field strength at that height are deduced. A radio source above a large sunspot shows a crescent shaped depression of circular polarization and a high brightness temperature. The emission mechanism is identified as gyroresonance at the second and the third harmonic layers and it is found that the second harmonic layer, where the magnetic field strength is 900 G, must be in the corona. An extended loop-like source connecting the leading and the following part of the active region as well as the sources associated with small spots are mainly due to thermal free-free emission by hot and dense plasma which is also observed in ultraviolet and soft X-ray radiation. The calculated radio brightness temperature, using the physical parameters deduced from the ultraviolet and soft X-ray line intensities, agrees with the observed brightness temperature. The height of the low brightness temperature sources above the small spots is 6000 ± 3000 km and that above the large spot is less than 3000 km: the source above the large spot does not show any shift relative to the sunspot due to the projection effect. Very strong radio emission was found which was associated with the merging of a group of small spots into the large sunspot. In the same day, warm ( 10⁶ K) and dense matter was present above the large spot. Evidence for nonthermal emission is presented.     

The efficiency of electron acceleration in solar type-IV radio pulsations with a zebra pattern

Based on a comprehensive analysis of the October 25, 1994 event, we consider the balance of energetic particles in a type-IV solar radio emission source with a zebra-type fine structure (in a coronal magnetic loop). The zebra pattern is formed through the injection of fast electrons into a trap and the formation of a ring-type nonequilibrium electron distribution function. We estimated the characteristic zebra-pattern lifetime, which is determined by the escape of fast particles from the trap into the loss cone. In addition, we determined the number of fast particles that must be injected into the trap to provide the observed radio brightness temperature in zebra-pattern stripes by analyzing the plasma emission mechanism responsible for the zebra-pattern generation. As a result, we estimated the efficiency of the electron acceleration mechanism in coronal magnetic loops at the post-flare evolutionary phase of an active region.