类太阳色球活动星εEri磁场的观测研究

本文给出１９９３—１９９４年期间，用云南天文台１米望远镜折轴摄谱仪观测获得类太阳色球活动星。εＥｒｉ的５个波段高分辨、高信噪比光谱，运用两种不同方法：谱线轮廓塞曼致宽分析和多重线统计分析法成功地测定了εＥｒｉ的表面磁场强度和磁场的覆盖因子，并对这两种磁场测定方法作了简单的讨论．     

Magnetic Reconnection, Turbulence, and Collisionless Shock

A short summary of recent progress in measuring and understanding turbulence during magnetic reconnection in laboratory plasmas is given. Magnetic reconnection is considered as a primary process to dissipate magnetic energy in laboratory and astrophysical plasmas. A central question concerns why the observed reconnection rates are much faster than predictions made by classical theories, such as the Sweet–Parker model based on MHD with classical Spitzer resistivity. Often, the local resistivity is conjectured to be enhanced by turbulence to accelerate reconnection rates either in the context of the Sweet–Parker model or by facilitating setup of the Pestchek model. Measurements at a dedicated laboratory experiment, called MRX or Magnetic Reconnection Experiment, have indicated existence of strong electromagnetic turbulence in current sheets undergoing fast reconnection. The origin of the turbulence has been identified as right-hand polarized whistler waves, propagating obliquely to the reconnecting field, with a phase velocity comparable to the relative drift velocity. These waves are consistent with an obliquely propagating electromagnetic lower-hybrid drift instability driven by drift speeds large compared to the Alfven speed in high-beta plasmas. Interestingly, this instability may explain electromagnetic turbulence also observed in collisionless shocks, which are common in energetic astrophysical phenomena.     

On the Line Formation in Stellar Magnetized Atmospheres

1 INTRODUCTIONIn the previous paper (on et al. 1999, hereafter Paper I), we investigated the wavelength-dependence of four colltribution functions (CFs) derived from dmerent formal solutions andreferring to different emergellt quantities in the unpolarized case. Because one cannot generallyassign a single formation region to the whole line band in a real stellar atmosphere, e.g., the solaratmosphere, instead, the line formation region can be defined as the layers deviating farthestfrom t…     

几个活动区精细H_α结构的物理浅析

本文利用紫金山天文台赣榆站太阳精细结构望远镜拍得的高分辨率色球Ｈ_α照片，分析了三个典型活动区。文中利用并检验了七十年代获得的磁图推导法则，应用自己的数值模拟知识和Ｚｗａａｎ对ＡＦＳ系新浮流区概括的特征，参考七十和九十年代总结的有关耀斑和ＥｌｌｅｒｍａｎＢｏｍｂ的出现规律，逐日分析活动区发展，定出其内部的中性线位置，提出简单和复合中性线的区分，由ＡＦＳ系和亮谱斑同时出现判断新浮流区，从近离带图找等离子体不稳定点，从远离带图找普遍的磁场流场分布，由Ｈ_α结构的综合迹象推测磁场变化。总结出有关活动区Ｈ_α结构、磁场及等离子体性质关系的几点启示。     

Ellerman Bombs,Type Ⅱ White—light Flares and Magnetic Reconnection in the Solar Lower Atmosphere

Ellerman bombs and type Ⅱ white-light flares share many common features despite the large energy gap between them.Both are considered to result from local heation in the solar lower atmosphere.This paper presents numerical simulations of magnetic reconnection occurring in such a deep atmosphere,with the aim to account for the common features of the two phenomena.Our numerical results manifest the following two typical characteristics of the assumed reconnection process:(1)magnetic reconnection saturates in-600-900s,which is just the lifetime of the two phenomens;(2)ionization in the upper chromosphere consumes quite a large part of the energy released through reconnection,making the heation effect most significant in the lower chromosphere.The applicationof the reconnection model to the two phenomena is discussed in detail.     

Chromospheric evolution and the flare activity of super-active region NOAA 6555

Super-active region NOAA 6555 was highly flare productive during the period March 21st–27th, 1991 of its disk passage. We have st udied its chromospheric activity using high spatial resolution Hα filtergrams taken at Udaipur along with MSFC vector magnetograms. A possible relationship of flare productivity and the variation in shear has been explored. Flares were generally seen in those subareas of the active region which possessed closed magnetic field configuration, whereas only minor flares and/or surges occurred in subareas showing open magnetic field configuration. Physical mechanisms responsible for the observed surges are also discussed.     

太阳活动区磁场观测的一种新方法

在太阳活动区的物理研究中,特别是在二维动力学光谱分析中,迫切需要相应活动区的磁图资料。本文介绍了在太阳光谱仪的入射狭缝后安装一种新型偏振器进行活动区二维磁场观测的新方法。这种方法不仅能获得日面上任一点的磁场强度,且可快速获得活动区的纵向场磁图。除此之外,还可利用多条谱线的同时观测,获得有关磁力线管结构等方面的资料。     

Spatially intermittent fields in photospheric magnetoconvection

Motivated by recent high-resolution observations of the solar surface, we investigate the problem of non-linear magnetoconvection in a three-dimensional compressible layer. We present results from a set of numerical simulations which model the situation in which there is a weak imposed magnetic field. This weak-field regime is characterized by vigorous granular convection and spatially intermittent magnetic field structures. When the imposed field is very weak, magnetic flux tends to accumulate at the edges of the convective cells, where it forms compact, almost 'point-like' structures which are reminiscent of those observed in the quiet Sun. If the imposed field is slightly stronger, there is a tendency for magnetic flux to become concentrated into 'ribbon-like' structures which are comparable to those observed in solar plages. The dependence of these simulations upon the strength of the imposed magnetic field is analysed in detail, and the concept of the fractal dimension is used to make a further, more quantitative comparison between these simulations and photospheric observations.