太阳大气中的光球亮点

首先是对太阳光球亮点近年来研究工作的总结。光球亮点是一种发生在太阳光球上宁静区域的的小尺度和短寿命增亮现象,平均直径在100～300knm之间,平均寿命约为几分钟。光球亮点的研究对于光球辐射和磁场性质的认识具有重要意义。过去的观测显示,绝大多数光球亮点的产生和演化与磁场,特别是光球上的小尺度磁场的演化密切相关,比如,两个同极性磁场的合并,或者反极性磁场的对消,或者一个同极性磁场的分裂,均可以促使光球亮点产生或消失。基于这样的观测结果,统计研究了2722个光球亮点(1600A)与光球上偶极磁元的关系,发现大约有1/3的光球亮点出现在偶极磁元中心附近。     

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。     

太阳异极性磁区的相互入侵

我们在文[1]的启发下,计算了磁中性线附近异极性磁区相互入侵(或挤压)引起的等离子体动力学问题。气体初态取用流行的宁静太阳光球色球大气模型,即非等温的密度指数变化的重力分层大气。采用Lagrangian格式数值求解自洽的MHD方程,这可使入侵力学变得直观明显——磁场随流体而运动。我们的新结果是入侵流动在光球低层产生出强的水平磁场(即强的横向场),但光球高层和色球低层的磁结构却变化不大,有力地支持了文[13]提出的光球色球里可能出现磁流体力学间断面的概念。入侵确实在磁中性线附近建立了电流片,但这电流片主要在光球低层,其量级和观测一致。另外还显示垂直下降运动也可能导致异极磁区的入侵。尽管在MHD~1方程里包含了电阻耗散和热传导流,但计算证明它们对入侵力学影响不大,热传导的作用只是使气体温度分布逐渐趋于宁静太阳分布(尽管高度变了)。     

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。     

太阳网络内磁场的研究

本论文可分为两个部分,第一部分系统地综述了太阳大气中的小尺度活动现象,并给出了详细的统计结果。小尺度磁场的对消激发小尺度活动现象。这些磁场显著影响太阳大气的结构和动力学特征,这产场影响能量从小阳大气的结构和动力学特征,如这些磁场影响能量从太阳大气的低层向高层传输,针状体动力学（小尺度磁活动）能够把物质从光球输送到日冕,及小尺度磁场对消产生的Ｘ射线亮点等等。近几年,大多数太阳物理学家认为小尺度磁场对     

AR5572中一个宁静暗条的缠绕运动与磁场的关系

1989年7月8日,在AR5572中,北京天文台怀柔太阳观测站观测到宁静日珥的缠绕运动。磁场观测表明,它与磁对消密切相关。     

1981年4月1日日面4N耀斑环系的光学前兆与活动特征

根据云南天文台太阳色球H_α和相应的光球黑子观测以及磁场测量,并结合有关X—ray资料等,对1981年4月1日日面4N大耀斑进行了部份测量和分析。结果表明,该耀斑为环系;光球浮现磁流和黑子扭曲、挤压和剪切运动是触发该耀斑的直接原因。而活动的黑子光桥又是浮现磁流的一种重要标志;耀斑环或带与磁场位形密切相关;耀斑后在运动空间原位置处光球又浮现出部份磁流;卵形暗条内预示能爆发大耀斑。     

色球磁场极性反转结构的某些观测特征

利用怀柔太阳观测站的３００余对球和色球的观测磁图，分析得出色球极性反转结构是存在于太阳大气中的真实物理现象的结论，根据对活动区两个层次上的磁场精细结构的分析，发现球磁场反转结构可能有４种不的存在形式。     

色球磁场极性反转结构的某些观测特征

利用怀柔太阳观测站的300余对光球(FeIλ5324.19A)和色球(H_βλ4861.34A)的观测磁图,分析得出色球极性反转结构是存在于太阳大气中的真实物理现象的结论.根据对活动区两个层次上的磁场精细结构的分析,发现色球磁场反转结构可能有4种不同的存在形式.     

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。     

Magnetic Flux Imbalance of the Solar and Heliospheric Magnetic Fields

A comparative analysis of solar and heliospheric magnetic fields in terms of their cumulative sums reveals cyclic and long-term changes that appear as a magnetic flux imbalance and alternations of dominant magnetic polarities. The global magnetic flux imbalance of the Sun manifests itself in the solar mean magnetic field (SMMF) signal. The north – south asymmetry of solar activity and the quadrupole mode of the solar magnetic field contribute the most to the observed magnetic flux imbalance. The polarity asymmetry exhibits the Hale magnetic cycle in both the radial and azimuthal components of the interplanetary magnetic field (IMF). Analysis of the cumulative sums of the IMF components clearly reveals cyclic changes in the IMF geometry. The accumulated deviations in the IMF spiral angle from its nominal value also demonstrate long-term changes resulting from a slow increase of the solar wind speed over 1965 – 2006. A predominance of the positive IMF B _z with a significant linear trend in its cumulative signal is interpreted as a manifestation of the relic magnetic field of the Sun. Long-term changes in the IMF B _z are revealed. They demonstrate decadal changes owing to the 11/22-year solar cycle. Long-duration time intervals with a dominant negative B _z component were found in temporal patterns of the cumulative sum of the IMF B _z .     

解决太阳横向磁场方向测定中180°不确定性的一个方法

本文提出了一种解决太阳横向磁场方向测定中１８０°不确定性的方法。该方法首先将Ｇａｒｙ等提出的方法定量化，客观地确定每一点的横场方向；然后由独立的Ｈ＿α观测或磁场演化历史，分析和确定磁力线的拓扑联接性，对客观确定的横场方向做经验修正。对活动区的应用表明，该方法是一个可供选择的解决横场方向不确定性的有效方法。     

全日面日冕磁场的计算：边界元法与级数法的比较

本文以线性无力场模式下边界元法（ＢＥＭ）为基础，根据Ｃａｒｒｉｎｇｔｏｎ１７３３—１７４２周的光球磁场观测数据，计算出相应各Ｃａｒｒｉｎｇｔｏｎ周日冕高度（２．５Ｒ＿⊙）全日面的太阳磁场。计算结果同势场模式下的级数解法（即待定系数法）的相应结果对比表明，两种方法都体现了较为一致的大尺度日冕磁场特征，但在数值上存在某些差异；有些Ｃａｒｒｉｎｇｔｏｎ周的磁中性线形状差异较明显；另外，两者都没有反映出光球磁场中原有的并在行星际空间探测到的中小尺度强磁场结构。本文最后指出了发展较精确的三维全日面磁场计算理论尚待解决的一些问题。     

The Magnetic Field Effect on Planetary Nebulae

In our previous work on the 3-dimensional dynamical structure of planetary nebulae the effect of magnetic field was not considered. Recently Jordan et al. have directly detected magnetic fields in the central stars of some planetary nebulae. This discovery supports the hypothesis that the non-spherical shape of most planetary nebulae is caused by magnetic fields in AGB stars. In this study we focus on the role of initially weak toroidal magnetic fields embedded in a stellar wind in altering the shape of the PN. We found that magnetic pressure is probably influential on the observed shape of most PNe.     

Nonlinear Force-Free Modeling of Coronal Magnetic Fields. II. Modeling a Filament Arcade and Simulated Chromospheric and Photospheric Vector Fields

We compare a variety of nonlinear force-free field (NLFFF) extrapolation algorithms, including optimization, magneto-frictional, and Grad – Rubin-like codes, applied to a solar-like reference model. The model used to test the algorithms includes realistic photospheric Lorentz forces and a complex field including a weakly twisted, right helical flux bundle. The codes were applied to both forced “photospheric” and more force-free “chromospheric” vector magnetic field boundary data derived from the model. When applied to the chromospheric boundary data, the codes are able to recover the presence of the flux bundle and the field’s free energy, though some details of the field connectivity are lost. When the codes are applied to the forced photospheric boundary data, the reference model field is not well recovered, indicating that the combination of Lorentz forces and small spatial scale structure at the photosphere severely impact the extrapolation of the field. Preprocessing of the forced photospheric boundary does improve the extrapolations considerably for the layers above the chromosphere, but the extrapolations are sensitive to the details of the numerical codes and neither the field connectivity nor the free magnetic energy in the full volume are well recovered. The magnetic virial theorem gives a rapid measure of the total magnetic energy without extrapolation though, like the NLFFF codes, it is sensitive to the Lorentz forces in the coronal volume. Both the magnetic virial theorem and the Wiegelmann extrapolation, when applied to the preprocessed photospheric boundary, give a magnetic energy which is nearly equivalent to the value derived from the chromospheric boundary, but both underestimate the free energy above the photosphere by at least a factor of two. We discuss the interpretation of the preprocessed field in this context. When applying the NLFFF codes to solar data, the problems associated with Lorentz forces present in the low solar atmosphere must be recognized: the various codes will not necessarily converge to the correct, or even the same, solution. On 07/07/2007, the NLFFF team was saddened by the news that Tom Metcalf had died as the result of an accident. We remain grateful for having had the opportunity to benefit from his unwavering dedication to the problems encountered in attempting to understand the Sun’s magnetic field; Tom had completed this paper several months before his death, leading the team through the many steps described above.     

太阳磁场的观测

分析了太阳的观测磁图所涉及的磁场位形 ,以及磁场观测研究中的一些问题。     

The Magnetic Field of the Solar Corona from Pulsar Observations

We present a novel experiment with the capacity to independently measure both the electron density and the magnetic field of the solar corona. We achieve this through measurement of the excess Faraday rotation resulting from propagation of the polarised emission from a number of pulsars through the magnetic field of the solar corona. This method yields independent measures of the integrated electron density, via dispersion of the pulsed signal and the magnetic field, via the amount of Faraday rotation. In principle this allows the determination of the integrated magnetic field through the solar corona along many lines of sight without any assumptions regarding the electron density distribution. We present a detection of an increase in the rotation measure of the pulsar J1801-2304 of approximately 170 rad m² at an elongation of 0.96° from the centre of the solar disc. This corresponds to a lower limit of the magnetic field strength along this line of sight of >41.8 nT. The lack of precision in the integrated electron density measurement restricts this result to a limit, but application of coronal plasma models can further constrain this to approximately 0.5 μT, along a path passing 2.7 solar radii from the solar limb, which is consistent with predictions obtained using extensions to the source surface models published by the Wilcox Solar Observatory.     

Influence of solar heliospheric parameters on cosmic rays anisotropy

In the present work the cosmic ray data of three different neutron monitoring stations, Deep River, Inuvik, and Tokyo, located at different geomagnetic cutoff rigidities and altitudes have been harmonically analyzed for the period 1980–95 for a comparative study of diurnal semi-diurnal and tri-diurnal anisotropies in cosmic ray intensity in connection with the change in interplanetary magnetic field Bz component and solar wind velocity on 60 quietest days. It is observed that the amplitudes of all the three harmonics increase during the period 1982–84 at all the stations during the high speed solar wind stream epoch and remain low during the declining phase of the stream. The amplitudes of the three harmonics have no obvious characteristics associated with the time variation of magnitude of the Bz component. The phases of all the three harmonics have no time variation characteristics associated with solar wind velocity and Bz. Published in Astrofizika, Vol. 49, No. 4, pp. 651–664 (August 2006).     

Resolving the Azimuthal Ambiguity in Vector Magnetogram Data with the Divergence-Free Condition: Theoretical Examination

We demonstrate that the azimuthal ambiguity that is present in solar vector magnetogram data can be resolved with line-of-sight and horizontal heliographic derivative information by using the divergence-free property of magnetic fields without additional assumptions. We discuss the specific derivative information that is sufficient to resolve the ambiguity away from disk centre, with particular emphasis on the line-of-sight derivative of the various components of the magnetic field. Conversely, we also show cases where ambiguity resolution fails because sufficient line-of-sight derivative information is not available. For example, knowledge of only the line-of-sight derivative of the line-of-sight component of the field is not sufficient to resolve the ambiguity away from disk centre.     

太阳磁场和速度场的研究

本文介绍了怀柔太阳学术集团于２２ 太阳周期间在太阳磁场和速度场研究方面的部分成果及对２３ 太阳活动周工作的展望