1980年2月16日日全食日冕白光和单色光观测——Ⅰ宁静日冕部分

本文叙述1980年2月16日云南日全食日冕白光和四个波段(波长为4700A、5303A、6000A及6374A)的单色光照像观测,侧重介绍宁静日冕部分的结果.文中给出了白光日冕的等光强图、椭率、冕洞和日冕凝聚区的位置以及几个方向上日冕单色光强度沿投影日心距的分布,导出了相应方向上日冕强度分布经验公式的系数、电子密度沿径向的分布和日冕的电子温度.     

1968年9月22日日食的日冕偏振观测

本文叙述1968年9月22日日全食所作的日冕偏振照相观测及资料分析结果。观测是用三物镜照相仪进行的,有效波段为5700—6300埃,有效波长为6000埃,仪器散射光很小(<1％)。光度测量得到1.1—3.5R_⊙的日冕绝对亮度和偏振;日冕接近极大型,东西南北都不十分对称;偏振的径向程度较好,赤道区平均偏振度在1.5—1.6R_⊙达到极大,P_(max)=0.45;全食时天空背景较亮(I_天=3.27×10~9H_⊙,P_天=20.7％,电矢量指向天顶),处理中作了相应改正,最后,采用平均日冕模型,计算了赤道区的电子密度和温度,并分离了K冕和F冕。     

国际日地空间探测剪影

①太阳风与地球磁层示意图②"地磁尾"卫星③"风"卫星(Wind)④4颗欧洲团星2号卫星在太空⑥SOHO于1998年4月7日11时拍摄的日冕物质抛射照片⑦"极"卫星于1998年4月11日1时拍摄跨越北美洲上空的极光暴⑧"极"卫星拍摄的极光椭圆     

1983年6月11日日全食光学观测

由北京天文台、紫金山天文台和南京天文仪器厂组成的中国日全食观测队天文组在1983年6月11日的日全食中成功地进行了下述几种项目的光学观测:(1)色球和日冕的光谱观测——拍摄波区为3600埃到6600埃,平均色散度约6.4埃/毫米,高度分辨率约110公里。(2)宽带日冕的光度及偏振观测。(3)日食全过程的彩色摄影。 本文对仪器结构、观测方法和获得的资料作了简要介绍。     

2004年1月8日活动区10537内耀斑和相关CME的分析研究

利用色球Hα线心像、TRACEUV和SOHO/EITEUV单色像、SOHO/LASCO白光日冕观测、SOHO/MDI光球磁图以及Nobeyama射电观测,对2004年1月8日日面边缘δ位形黑子群AR10537内发生的一个M1.3耀斑及相关的CME进行了初步的分析。该耀斑除了位于反极性磁场区域、覆盖部分黑子半影的两个主耀斑带外,还伴随有一个明显的远距离耀斑带,这表明有扰动能量沿大尺度日冕结构从耀斑源区向外传播。这一远区增亮处随后有EITdimming出现,表明色球蒸发导致的物质损失可能是产生日冕dimming的重要因素。另外,位于远距离耀斑带南面的一个大宁静暗条在耀斑发生后有部分消失,这可能与该耀斑导致的大尺度日冕磁场重构有关。该耀斑爆发与LASCO观测到的一个快速partialhaloCME在空间和时间上具有密切的关系,它们极可能是相同磁场过程在日冕的不同表现,故我们将此耀斑及与之伴随的日冕dimming认证为这一CME的日面源区。     

1986年2月4日特大耀斑的物理先兆

本文从光球、色球及源于日冕的射电噪暴观测资料出发,分析了1986年2月4日4日级低年大耀斑的爆发前兆特征,可供耀斑物理预报及低年大耀斑物理机制的研究参考。     

1998年9月23 日复杂太阳爆发射电联合观测的初步分析

利用北京天文台1998.09.23日1-2GHz和2.6-3.8GHz频谱仪观测到的一个Ⅲ-Ⅳ型复杂大爆发，结合俄罗斯SSRT和德国分米-米波动态频谱仪的观测资料，进行了初步的比对分析，拓展了关于日冕电子加速和日冕磁结构方面的一些研究内容，简单地注释了一些可研究的现象和运动Ⅳ型爆发及多重脉动的辐射机制。     

1997年3月9日的日冕偏振CCD观测

给出１９９７年３月９日日全食时所作的日冕偏振ＣＣＤ观测资料的处理结果,包括太阳赤道东西和两极等十二个方向的中冕（１．６－３．２Ｒ）绝对亮度分布和偏振度分布。     

1997年3月9日的日冕偏振CCD观测

给出１９９７年３月９日日全食时所作的日冕偏振ＣＣＤ观测资料的处理结果,包括太阳赤道东西和两极等十二个方向的中冕（１．６￣３．２Ｒ⊙）绝对亮度分布和偏振度分布。     

日冕物质抛射的偏转特性研究

日冕物质抛射(CME)是巨大的、携带磁力线的泡沫状气体,在几个小时中被从太阳抛射出来的过程。日冕物质抛射伴随着大量带电粒子和辐射的释放,这些物质进入日地空间,对日地空间的磁场造成很大扰动;当它们传播到地球附近时,则严重影响地球的磁场,产生磁暴,也对空间和地面的电子设备造成干扰。日冕物质抛射在传播过程中如果发生偏转,将影响它对地有效性。因此研究日冕物质抛射的偏转特性,对预报日冕物质抛射对日地空间的影响具有重要意义。主要利用2007年10月8日STEREO卫星的日冕物质抛射观测资料,结合全日面线性无力场模型(Global Linear Force-Free Field,GLFFF)进行磁场外推,分析日冕物质抛射偏转与背景磁场能量密度分布之间的关系,并计算日冕物质抛射的运动轨迹。通过改变无力因子α,发现当α=0.15时,计算得到的日冕物质抛射运动轨迹与实际观测的日冕物质抛射运动轨迹拟合得最好。     

Coronal line intensity as an integrated index of solar activity

The relation between coronal green line intensity and high-speed streams of solar wind emitted by coronal holes or by loop structures of the corona is studied. As well as these exclusive regions of coronal radiative emission, other factors of solar activity have been taken into account in this relation, such as proton events, sunspot number, faculae, and solar magnetic fields.Although the investigated time period (1964–1974) is very short, because of lack of data, we attempted to define the intensity of the coronal green line as an integrated index of the solar activity which can express all the photospheric and coronal phenomena of the Sun. The contraction of the low-density coronal-hole regions and the presence of bright loops during solar maximum provide a theoretical explanation of the above-mentioned relation.     

日冕磁场重建方法在研究太阳爆发活动中的应用

太阳是与地球关系最为密切的天体.发生在日面上的剧烈爆发性活动可能对人类的生存环境产生巨大影响甚至是灾难性后果.包含太阳耀斑、暗条爆发和日冕物质抛射在内的太阳爆发活动是同一物理过程的不同表现形式,其能量来源于爆发前储存在日冕中的磁场自由能.因此,了解日冕磁场的3维结构是理解太阳爆发的触发机制以及活动区的稳定性等现象的前提.由于观测技术限制,目前尚无法对日冕磁场进行常规观测,因此发展了多种利用可常规观测的光球磁场来重建日冕磁场的方法.主要评述近10 yr来各种日冕磁场重建方法在研究太阳爆发活动中的应用.     

Studying Solar Eruptions from Reconstructed Coronal Magnetic Field

The Sun is the celestial body in the sky with the closest relationship with the Earth. The violent eruptive activities happening on the Sun can greatly impact the human living environment and lead to disastrous consequences. It is well accepted that solar eruptions including the solar flare, prominence eruption and coronal mass ejection are the different manifestations of a single physical process powered by the magnetic free energy gradually stored in the corona prior to eruptions. Therefore, mapping the three-dimensional structure of coronal magnetic field is a prerequisite to understand the initiation mechanism of solar eruptions. Due to the technological and methodological difficulties, routine observations of the coronal magnetic field are still unavailable. Therefore, a number of methods have been developed to reconstruct the coronal magnetic field. This paper mainly reviews the applications of various reconstruction methods to the studies of the solar eruptions in the recent ten years.     

Probing the Fundamental Physics of the Solar Corona with Lunar Solar Occultation Observations

Imaging and spectroscopy of the solar corona, coupled with polarimetry, are the only tools available at present to capture signatures of physical processes responsible for coronal heating and solar wind acceleration within the first few solar radii above the solar limb. With the recent advent of improved detector technology and image processing techniques, broad-band white light and narrow-band multi-wavelength observations of coronal forbidden lines, made during total solar eclipses, have started to yield new views about the thermodynamic and magnetic properties of coronal structures. This paper outlines these unique capabilities, which until present, have been feasible primarily with observations during natural total solar eclipses. This work also draws attention to the exciting possibility of greatly increasing the frequency and duration of solar eclipse observations with Moon orbiting observatories utilizing lunar limb occultation of the solar disk for coronal measurements.     

Evolving coronal holes and interplanetary erupting stream disturbances

Coronal holes and interplanetary disturbances are important aspects of the physics of the Sun and heliosphere. Interplanetary disturbances are identified as an increase in the density turbulence compared with the ambient solar wind. Erupting stream disturbances are transient large-scale structures of enhanced density turbulence in the interplanetary medium driven by the high-speed flows of low-density plasma trailing behind for several days. Here, an attempt has been made to investigate the solar cause of erupting stream disturbances, mapped by Hewish & Bravo (1986) from interplanetary scintillation (IPS) measurements made between August 1978 and August 1979 at 81.5 MHz. The position of the sources of 68 erupting stream disturbances on the solar disk has been compared with the locations of newborn coronal holes and/or the areas that have been coronal holes previously. It is found that the occurrence of erupting stream disturbances is linked to the emergence of new coronal holes at the eruption site on the solar disk. A coronal hole is indicative of a radial magnetic field of a predominant magnetic polarity. The newborn coronal hole emerges on the Sun, owing to the changes in magnetic field configuration leading to the opening of closed magnetic structure into the corona. The fundamental activity for the onset of an erupting stream seems to be a transient opening of pre-existing closed magnetic structures into a new coronal hole, which can support highspeed flow trailing behind the compression zone of the erupting stream for several days.     

Differential Rotation of the Solar Corona from Magnetic Field Data

A method for investigating the differential rotation of the solar corona using the coronal magnetic field as a tracer is proposed. The magnetic field is calculated in the potential approximation from observational data at the photospheric level. The time interval from June 24, 1976, to December 31, 2004, is considered. The magnetic field has been calculated for all latitudes from the equator to ±75? with a 5? step at distances from the base of the corona 1.0 R_⊙ to 2.45 R_⊙ near the source surface. The coronal rotation periods at 14 distances from the solar center have been determined by the method of periodogram analysis. The coronal rotation is shown to become progressively less differential with increasing heliocentric distance; it does not become rigid even near the source surface. The change in the coronal rotation periods with time is considered. At the cycleminimumthe rotation has been found to bemost differential, especially at small distances from the solar center. The change in coronal rotation with time is consistent with the tilt of the solar magnetic equator. The results from the magnetic field are compared with those obtained from the brightness of the green coronal Fe XIV 530.3 nm line. The consistency between these results confirms the reliability of the proposed method for studying the coronal rotation. Studying the rotation of the coronal magnetic field gives hope for the possibility of using this method to diagnose the differential rotation in subphotospheric layers.     

An empirical model of the daily evolution of the coronal index

Global changes of the solar activity can be expressed by the coronal index that is based upon the total irradiance of the coronal 530.3 nm green line from observations at five stations. Daily mean values of the coronal index of solar activity and other well-correlated solar indices are analyzed for the period 1966–1998 covering over three solar cycles. The significant correlation of this index with the sunspot number and the solar flare index have led to an analytical expression which can reproduce the coronal index of solar activity as a function of these parameters. This expression explains well the existence of the two maxima during the solar cycles taking into account the evolution of the magnetic field that can be expressed by some sinusoidal terms during solar maxima and minima. The accuracy between observed and calculated values of the coronal index on a daily basis reaches the value of 71%. It is concluded that the representative character of the coronal index is preserved even when using daily data and can therefore allow us to study long-term, intermediate and short-term variations for the Sun as a star, in association with different periodical solar–terrestrial phenomena useful for space weather studies.     

Solar Corona: from Shklovsky to our Days

Fundamental advances in the physics of the solar corona from the 1960's to the present time are briefly reviewed. Progress in coronal investigations has mainly been associated with major space missions, which have discovered such new phenomena as coronal holes and coronal mass ejections, and have enabled detailed study of coronal arch systems. The role of magnetic fields on various scales in quasi-steady-state phenomena is discussed for various phases of the solar activity cycle.     

Long-term modulation of the coronal index of solar activity

Monthly mean values of the coronal index of solar activity and other solar indices are analyzed for the period 1965–1997 covering three solar cycles. The coronal index is based upon the total irradiance of the coronal 530.3 nm green line from observations at five stations. The significant correlation of this index with the sunspot number and the number of the grouped solar flares have led to an analytical expression which can reproduce the coronal index of solar activity as a function of these parameters. This expression well explains the existence of the two maxima during the solar cycles taking into account the evolution of the magnetic field that can be expressed by a sinusoidal term with a 6-year period. The agreement between observed and calculated values of the coronal index on a monthly basis is high enough and reaches the value of 92%. It is concluded that the coronal index can be used as a representative index of solar activity in order to be correlated with different periodic solar–terrestrial phenomena useful for space weather studies.     

Manifestation of solar activity in solar wind particle flux density

An analysis has been made of the origin of long-term variations in flux density of solar wind particles (nv) for different velocity regimes. The study revealed a relationship of these variations to the area of the polar coronal holes (CH). It is shown that within the framework of the model under development, the main longterm variations of nv are a result of the latitude redistribution of the solar wind mass flux in the heliosphere and are due to changes in the large-scale geometry of the solar plasma flow in the corona.

A study has been made of the variations of nv for high speed solar wind streams. It is found that nv in high speed streams which are formed in CH, decreases from minimum to maximum solar activity. The analysis indicates that this decrease is attributable to the magnetic field strength increase in coronal holes.

It has been found that periods of rapid global changes of background magnetic fields on the Sun are accompanied by a reconfiguration of coronal magnetic fields, rapid changes in the length of quiescent filaments, and by an increase in the density of the particle flux of a high speed solar wind. It has been established that these periods precede the formation of CH, corresponding to the increase in solar wind velocity near the Earth and to enhancement of the level of geomagnetic disturbance.