太阳网络内磁场的研究
文献类型：学位论文
| 作者 | 张军 |
| 学位类别 | 博士 |
| 答辩日期 | 1999 |
| 授予单位 | 中国科学院云南天文台 |
| 授予地点 | 昆明 |
| 导师 | 汪景琇 |
| 关键词 | 太阳物理学 小尺度磁场 网络内磁场 |
| 中文摘要 | 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，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日冕加热有重要意义。第二部分包括了对网络内磁场的系统研究。其中大多数结果是第一次被发现。近几年来，利用美国大熊湖天文台和北京天文台怀柔观测站的高分辨率磁图，网络内磁场的研究取得了重大进展。1．网络内磁元的寿命。由于磁图的高时间分辨率和高灵敏度，使得我们第一次能够准确地测量网络内磁元的寿命。网络内磁元的寿命从10分钟一直上升到7.5小时，平均寿命为2.1小时。2．网络内磁元的演化。利用磁图，我们跟踪了528个磁元，包括它们的产生和消失方式。我们发现，网络内磁元的产生有以下几类：一半磁元的是以混合极性的‘一束’不可分辨的磁通量元上浮；五分之一是以瞬现区（微双极区）的形式浮现；五分之一是以几个相同极性的网络内元的合并产生；另个的十分之一是由较大的网络内元分裂产生的。网络内磁元的消失也可分为以下四类：三分之一网络内磁元通过磁对消的方式消失掉；三分之一以衰变的方式消失；四分之一通过与相同极性的网络或网络内磁元而消失；另外的十分之一分裂成更小的磁元。由于网络磁元和网络内磁元不断的相互作用，我们可以认为网络内磁元的磁通量对网络磁元磁通量有贡献，网络磁元的磁通量并不完全由衰变活动区磁通量提供。3．网络内磁元的速度场。网络内磁元速度场的研究有很重要的意义，它能够反应太阳表面超米粒流场的主要特征。由于受观测资料的限制，使得网络内磁元的速度场测量非常困难。我们从两个方面测量速度场：（1）选取一定时间间隔的两幅磁图，在磁图中比较规则的超米粒元胞内，测量磁元在这些超米粒元胞内不同位置上的径向速度v_r和环向速度v_c。（2）在不同时间间隔内跟踪网络内磁元，测量它们在超米粒元胞内不同位置上的v_r和v_c。我们发现，太阳表面超米粒元胞的速度场在大尺度上存在规则分布。这一发现可能对太阳物理有很重要的意义，可以用它来解释电流螺度和磁场螺度的规则分布：规则运动的速度场产生规则的电流分布和磁场分布。当然太阳活动现象的复杂性不可能用简单的对应关系来说明，而且的速度场螺度的了解还非常肤浅，进一步的深入研究显得非常必要。4．对超米粒元胞上网络上网络磁通量和网络内磁通量的极性分布进行了统计研究，发现在大多数情况下，网络磁通量和网络内磁通量的极性相反。我们第一次提出网络磁场和网络内磁场具有拓扑连接性。5．理论方面，讨论了尺度磁流管的稳定性问题，第一次提出磁流管内的气压的变化能够稳定磁流管，并给出了数值模拟结果，提出了磁流管的稳定性判据。 |
| 英文摘要 | This thesis consists of two parts. Part I is a review of small-scale activity phenomena in solar atmosphere. These phenomena are: (1) jets, including spicules, macrospicules, Hα jets, EUV jets, and X-ray; (b) bright (dark) point features, such as network bright points, X-ray bright points, microwave bright points, magnetic bright points, and He 1 10830 A dark points; (c) explosive phenomena (e.g., transition region explosive events, mini-filament eruption); (d) transient brightenings and EUV blinkers; (e) MHD turbulent events; (f) microflares and nanoflares. The properties of these active phenomena are carefully described and the theoretical inter-pretations are also presented. Part II is a series papers on the properties of intranetwork (IN) magnetic elements using the best magnetograms on quiet-Sun ever obtained by Big Bear Solar Observatory (BBSO) and Huairou Solar Observation Station (HSOS). Most of the results presented in this dissertation are new findings obtained mainly by the author. In Paper 1, we present the lifetime of IN elements for the first time. The lifetime ranges from 0.2 hour to 7.5 hour, with a mean lifteim at 2.1 hour. Paper 2 describes the velocity fields of IN elements. By tracing individual elements, we have measured horizontal velocity and studied motion patterns of Intranetwork (IN) magnetic elements for the first time. The magnetograms obtained at Big Bear Solar Observatory span an interval of 10-hour and cover an area of 310 * 240 arc sec~2. In general, In elements move radially and isotropically outwards from emergence centers to boundaries of supergranule cells at first. However, when they reach halfway between cell centers and boundaries, the motion of IN elements is non-isotropic, there are prior directions. Most of IN elements move towards the edges of network elements. There are two components of the velocity fields: radial velocity and circular velocity. From the centers to the boundaries of supergranule cells, the magnitude of the radial velocity decreases gradually; but that of the circular velocity increases obviouslys, at halfway between cell center and boundary, the circular acceleration reaches the maximum, about 10~(-1) m s~(-2). The mean circular velocity near the boundary is about 0.4 km s~(-1). The horizontal speeds deduced by tracing 768 intranetwork elements range from 0.05 km s~(-1) to 0.8 km s~(-1) with a peak distribution at 0.4 km s~(-1). Both within the supergranule cells and on the boundaries, there are convergence centers, but divergence centers always exist within supergranule cells. There seems to be a regular distribution of IN velocity fields on large-scale range of solar surface. This research is also the begining work. The regular distribution of velocity fields can be used to interpret the regular distribution of current helicity and magnetic field helicity on different aspects. The appear patterns and disappear patterns of IN elements are especially studied in Paper 3. The appearance of IN elements can be classified into the following categories: half of the total IN elements emerge as clusters of mixed polarities somewhere within the network cells, one fifth appear as ephemeral regions (tiny bipoles), one fifth result from the merging of several elements of a given polarity, and one tenth appear by fragmentation of larger elements. IN elements disappear in four ways: one third of total IN elements cancel with elements of opposite polarity, one third decay into weak fields without apparent interaction with other elements, one fourth merge with IN or network elements of the same polarity, and one tenth split into smaller IN elements below detecting limit. About one ninth (one sixth) of the IN elements merge (cancel) with network features, consequently, part of the flux in network features is built up from former IN magnetic flux, and part is eliminated by IN elements. The net effect of merging and cancellation is a gradual reduction of the total flux of network elements in the 10 hours observational interval. It seems that not all the network magnetic flux is the remnant of active region magnetic flux. In Paper 4, we have studied the polarity distribution of intranetwork and network fields. Using very deep magnetograms obtained at Huairou Solar Observation Station (HSOS) and Big Bear Solar Observatory (BBSO). We are able to determine 100 network cells and measure the polarities of IN and network magnetic flux within each cell. The analysis reveals that In enhance networks, about 90% of IN and network magnetic flux are opposite polarity; in mixed-polarity network, 75% are opposite polarity. We point out firstly that IN fields and network fields are connected topologically, although they are much different on many aspects. In theory, we have studied the stability of small magnetic flux tube. One of the most important stability of plasma physics is interchange instability. On the study of small flux tubes stability, we first consider the stabilizing effects of supergranular velocity fields, twists of magnetic field-lines, gas pressure and gas pressure gradient interior of flux tubes, and we have given the following results: on the solar conditions, velocity fields, twists of field-lines and internal gas pressure stabilize flux tubes. |
| 学科主题 | 天文学 |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 页码 | 158 |
| 源URL | [http://ir.ynao.ac.cn/handle/114a53/4360]  |
| 专题 | 云南天文台_其他 |
| 推荐引用方式 GB/T 7714 | 张军. 太阳网络内磁场的研究[D]. 昆明. 中国科学院云南天文台. 1999. |
入库方式： OAI收割
来源：云南天文台
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