暗条手征性和磁场位形研究

发布时间：2018-04-23 05:22

本文选题：暗条 + 手征性　；参考：《南京大学》2017年博士论文

【摘要】：暗条是太阳大气中非常显著的活动现象,它的爆发与耀斑和日冕物质抛射(CME)等现象密切相关,反映了太阳大气中磁能的失稳和释放过程,而它的形态特征也与磁场的结构有关联。因此,暗条的形态特征为我们诊断日冕磁场提供了一个特殊的窗口。太阳磁场的螺度呈现比较显著的南北半球不对称性,北半球以负螺度为主,南半球正螺度占优。但是,关于半球规则的强度及其随时间的变化规律还存在很大争议。暗条的手征性是表征太阳磁场螺度的一个参量。为了揭示暗条手征性半球规则强度随时间的变化规律,本文选取在2010年5月至2015年12月之间发生在日面上的爆发暗条为研究样本(共571个事件),利用爆发暗条落点偏向识别暗条手征性。该时段涵盖第24太阳活动周上升段和下降段早期。统计结果显示,该时段91.6%的爆发暗条遵守螺度符号半球规则。约97%宁静暗条在太阳活动周上升段遵守半球规则,在活动周下降段降低为～85%;中间型暗条在整个统计时段保持很高的半球规则符合度,约96 ±4%。只有活动区暗条表现出明显的波动,在活动周上升段半球规则符合度由～63%升高到～95%,在活动周下降段保持在82 ±5%左右,但是在太阳极大年附近的半年内,其螺度符号半球规律几乎消失。此外,我们从磁场演化角度对样本中反半球规则暗条的形成进行了分析,分析结果显示反半球规则暗条源于跨赤道螺度传输、磁流浮现、太阳表面磁流扩散、湍流运动以及高纬度区较差自转。在暗条手征性统计的基础上,我们利用基于暗条落点增亮的间接方法对暗条的磁场位形进行识别。结果显示,暗条样本中～89%属于反转极性暗条,由磁绳结构支撑;～11%属于正常极性暗条,由磁拱结构支撑。在暗条磁场位形研究基础上,我们试图讨论争议已久的2个有关CME的问题。一是关于磁绳是否是CME前身结构的必要条件。我们的观点是磁绳不是必要条件,即～89%的CME其前身结构为磁绳,而约～11%的CME其前身结构为剪切磁拱。对于后者,剪切磁拱会在爆发过程中通过磁重联形成磁绳。二是关于CME的速度是否与暗条磁场位形有关。我们的结果显示磁场位形对CME的抛射速度几乎没有影响,是爆发源区的磁场强度决定了 CME的抛射速度。最后,我们利用珥震学对暗条经典倒钩的磁场位形进行了验证,结果表明经典的倒钩和主干一样,物质由磁凹陷支撑。但是,支撑主干的磁凹陷曲率半径数倍大于倒钩末端磁凹陷曲率半径,支撑倒钩的磁凹陷曲率半径随着高度的增加而增大,最终与主干的磁凹陷曲率半径趋于一致。此外,我们发现存在第二类倒钩,其末端不同于经典倒钩,并不向下延伸,也不对应寄生磁极或局部磁中性线,它们是由主干伸出的一簇暗条纤维组成,末端通常向上延伸。并指出暗条纵向振荡是第二类倒钩一种可能的形成机制。
[Abstract]:The dark strip is a very significant active phenomenon in the solar atmosphere. Its outburst is closely related to the phenomena such as flare and coronal mass ejection (CME), which reflects the instability and release process of magnetic energy in the solar atmosphere. Its morphological characteristics are also related to the structure of the magnetic field. Therefore, the morphological features of the dark strip provide a special window for us to diagnose the coronal magnetic field. The helicity of the solar magnetic field shows obvious asymmetry in the north and south hemispheres. The negative helicity is dominant in the northern hemisphere and the positive helicity is dominant in the southern hemisphere. However, the intensity of hemispheric rules and their variation over time are still controversial. The chirality of the dark strip is a parameter to characterize the helicity of the solar magnetic field. In order to reveal the rule that the regular strength of chiral hemispheres varies with time, From May 2010 to December 2015, a total of 571 outburst dark strips were selected to identify the chirality of dark strips. This period covers the ascending and early stages of the 24 th solar cycle. The statistical results show that 91.6% of the outbursts follow the hemispherical rules of helicity symbols. About 97% of the quiet strips followed the hemispheric rule in the rising phase of the solar cycle, and decreased to 85 at the descending stage of the active cycle, while the middle type strip maintained a high hemispherical consistency of 96 卤4 in the whole statistical period. Only the dark strip of the active region showed obvious fluctuation, and the hemispheric regularity of the ascending segment of the active cycle increased from 63% to 95%, and remained at about 82 卤5% in the decreasing segment of the active cycle, but within half a year of the maximum solar year, The hemispherical regularity of the helicity symbol almost disappeared. In addition, from the angle of magnetic field evolution, we analyze the formation of the anti-hemispheric rule strip in the sample. The results show that the anti-hemispheric rule strip originates from the transequatorial helicity transmission, the magnetic current emerges, and the magnetic current diffuses on the surface of the sun. Turbulent motion and poor rotation at high latitudes. On the basis of the chirality statistics of dark strips, we use the indirect method based on the bright spot of dark strips to recognize the magnetic field configuration of dark strips. The results show that 89% of the dark strip samples belong to reverse polarity dark strip, 11% belong to normal polar dark strip supported by magnetic rope structure, and supported by magnetic arch structure. Based on the study of dark strip magnetic field configuration, we try to discuss two controversial CME problems. The first is about whether the magnetic rope is a necessary condition for the former structure of CME. Our view is that magnetic rope is not a necessary condition, that is, 89% of CME is magnetic rope, while about 11% of CME has shear arch. For the latter, the shear magnetic arch will form a magnetic rope by magnetic reconnection during the explosion. The second is whether the velocity of CME is related to the configuration of dark strip magnetic field. Our results show that the configuration of the magnetic field has little effect on the ejection velocity of CME, and that the intensity of the magnetic field in the source region of the burst determines the ejection velocity of the CME. Finally, we verify the magnetic field configuration of the classical barbs by means of prominence seismology. The results show that the classical barbs are supported by magnetic depressions just like the main barbs. However, the curvature radius of the magnetic sag supporting the main stem is several times larger than that of the magnetic sag at the end of the barb, and the curvature radius of the magnetic sag supporting the barb increases with the increase of height, which tends to be consistent with the curvature radius of the magnetic sag in the main stem. In addition, we find that there is a second kind of barbs, whose ends are different from classical barbs and do not extend downwards, nor do they correspond to parasitic magnetic poles or local magnetic neutral lines. They are composed of a cluster of dark fibers extending out of the trunk, and the ends usually extend upward. It is also pointed out that the longitudinal oscillation of dark strip is a possible mechanism of the second kind of barbed hook.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P182

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