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太阳半径周期分析及物理机制研究
Alternative TitleResearch on the Periodicities and Physical Mechanism of Solar Radius
屈智宁
Subtype博士
Thesis Advisor李可军
2015-07-01
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline天体物理
Keyword太阳物理 太阳半径 半径测量 半径变化
Abstract太阳是距离地球最近的一颗恒星,也是人类唯一可以进行高分辨率成像观测和研究的恒星。太阳没有岩石类行星那样具有一个明确的边界。一般而言, 太阳半径是指从太阳球心到光球层外边界的距离。对于标准太阳模型,太阳半 径是指波长 λ =5000?A 时光学深度 τ5000 = 1 所对应的层次。中国是世界上第 一个测量太阳半径的国家,可以追溯到公元前一世纪。系统性测量始于 19 世 纪,其标准值为 959.63” 。主要有以下几种测量方法:(1) 子午圈测量;(2) 日 食和水星凌日;(3) 望远镜漂移扫描技术;(4) 等高仪方法;(5) 卫星角距离测 量。太阳半径的研究,主要集中于以下三类观点:一是认为太阳半径在缩小; 二是认为太阳半径没有变化;三是认为太阳半径变化与一些太阳活动指数有关 联,并具有自身的运动规律。太阳半径是否变化,如何变化,目前尚无定论。 本文首先回顾了历史上测量太阳半径的方法,对测量数据的结果进行了分析, 总结。接着选取了地基设备中历史上连续性最长的一组数据(法国 Calern 天文 台 1975 年至 2006 年观测资料)和测量数据密度较大的一组数据(巴西 Rio de Janeiro 天文台 1998 年至 2009 年观测资料)进行分析研究。针对数据本身的 特点,在研究手段上采用了经验模态分解(EMD),日期补偿离散傅里叶变化 方法(DCDFT),CLEANest 和 Lomb–Scargle 算法相结合的非线性分析方法。 主要结果如下: 1、运用法国 Calern 天文台 1978 年 2 月至 2000 年 9 月的观测资料,采用 Lomb–Scargle 算法和日期补偿离散傅里叶变化方法(DCDFT)来探求太阳半 径变化的周期性,得到具有统计意义的 3 类周期: 1年,2.6 年和11年。我们利 用Nandy & Choudhuri 提出的发电机模型,认为黑子逐渐增多的过程中,对流 层底部的磁流管逐渐减弱,太阳活动极大年是对流层底部磁流管相对更弱的时 期;此时,由于磁流管变弱,磁压减小,从而引起该区域塌缩,导致太阳半径 变小。反之,在太阳活动极小年时,对流层底部磁流管变强,磁压增大,从而 引起该区域膨胀,导致太阳半径变大。磁压的增大和减小导致了该区域的膨胀 与收缩,从而影响了太阳半径的变化。另一方面,太阳半径变化趋势与太阳活 动呈现反相位关系在太阳半径与黑子数的月平均交叉相关系数中得到了体现。 因此,对流层底部约束的磁流管内部磁压的变化导致了太阳半径 11年周期的变化,这种变化与黑子周期是反相位的。 2、结合法国 Calern 天文台与巴西 Rio de Janeiro 天文台太阳半径观测资 料,采用了经验模态分解(EMD),日期补偿离散傅里叶变化方法(DCDFT), CLEANest 和 Lomb–Scargle 算法。分别计算了两组数据的周期值,并与其他 太阳半径观测资料进行了比较。结果显示不同设备的观测资料得出了类似的结 果,表明了太阳半径变化的固有性。而原始数据与修正大气扰动造成的干扰因 素后的数据比较,得出了类似的周期值;则表明了地面设备测量太阳半径的可 靠性。 3、对太阳半径自转周期进行了研究,并把太阳半径观测资料与黑子面积 联系起来,探讨了磁场对太阳半径变化的作用。在采用自相关分析方法分别得 到两组数据的自转周期信号基础上,将带来自转周期信号的正弦函数拟合每 年的太阳半径数据;并计算了拟合函数与原始数据之间的相关系数。结果显示 在绝大多数的年份,太阳半径的自转周信号具有高度统计意义。这表明自转周 期信号的确存在于太阳半径变化周期中。另一方面,自转周期信号的太阳半径 正弦函数与对应的黑子面积进行了相关分析,可以发现:所有具有统计意义的 相关系数都是负数,表明了太阳半径自转周期变化与黑子面积是反相位的;而 且,在太阳活动极大年时期的相关系数绝对值大于太阳活动极小年时期的相关 系数。这表明了强磁场对太阳半径自转周期变化的抑制作用大于弱磁场。太阳 表层的磁场干扰对流运动,引起热传输效率的下降,其作用间接对太阳半径变 化起到相反效果。同时,强磁场会引起磁张力的增加,这将会导致压缩太阳表 层区域。因此,在太阳活动极大年,表层磁场干扰对流作用更明显,引起热传 输效率的下降,对太阳半径变化的间接作用以及磁张力的增加都会更强的抑制 太阳半径自转周期变化。 最后,总结了本文研究的内容,指出太阳半径变化研究中存在的问题。并 提出下一步可能开展的研究方向。
Other AbstractThe Sun is the nearest star to our earth, the only one high-resolution imaging observed and studied in the universe. The Sun does not have a clear boundary,like those of rocky planets. Usually, the photosphere solar radius is de?ned as the distance from the center of the Sun to the outer boundary of the photo- sphere. China was the ?rst country in the world to measure it, which can date back to West Han Dynasty in about 1st century B. C. The solar radius has been measured systematically since 19th century. The standard solar radius value of 959.63” adopted by the IAU was ?rst obtained by Auwers. Since then, a variety of instruments and di?erent methods have been used to measure it: (1)Solar eclipses and Mercury transit, (2) Meridian circle measurements, (3) Driftscan technology, (4) Solar astrolabes, (5) Satellite direct angular measurements.Either from the ground or from orbit. However, the measured results are inconsistent. Some researchers have reported that the solar radius had shown a secular decrease. Other researchers have reported that the solar radius is stationary. Some researchers have found that the radius ?uctuates over periods of a decade days to several years. The thesis, ?rstly, introduces the history measurement of the solar radius and progress study of the solar radius, then several nonlinear analysis approaches are used to study the periodicities of solar radius data ob- tained in the Calern Observatory and Rio de Janeiro Observatory. The purpose of these analyses is to gain some physical understanding of the observation and the main results are listed as follows: 1. In order to study the long period variations of the solar radius, daily solar radius data from 1978 February to 2000 September obtained at the Calern Observatory are used. Continuous measurements of the solar radius are di?cult due to the weather, seasonal e?ects, and instrument characteristics. Thus, to analyze these data, we ?rst use the Dixon criterion to reject outliers, then we measure the cross-correlation between the solar radius and sunspot numbers. The result shows that the solar radius is antiphase with the sunspot numbers and shows lead times of 74 months relative to the sunspot numbers. Two nonlinear analysis methods including Lomb–Scargle and date compensated discrete Fourier transform are also applied to investigate the periodicity of the solar radius. Both methods yield similar signi?cance periodicities around ~ 1 yr, ~ 2.6 yr, and ~ 11yr. We discussed the possible mechanisms for these periods. The possible physical cause of the ~ 11 yr period is the cyclic variation of the magnetic pressure of the concentrated ?ux tubes at the bottom of the solar convection zone. 2. Combining the data of daily solar radius measured at Calern Observatory (R c ) and Rio de Janeiro Observatory (R r ), di?erent nonlinear analysis methods including EMD, DCDFT, CLEANest and Lomb–Scargle are used to study the periodicityies of these two data. The results are consistent with several former peridodicies obtained in other solar radius data. It indicates that di?erent periodicityies do exist in solar radius. On the other hand, spectra analysis for both raw data for no correction and corrected data for seeing e?ect shows that spectra peak are signi?cant. If atmospheric turbulence drives the ground-based solar radius measurements, both spectra can not get similar peaks. Thereby, ground-based solar radius measurements are valuable for probing solar radius variations. 3. We consider the solar radius in conjunction with sunspot areas to discuss the variation of the solar radius, and how magnetic ?elds a?ect the variation of the radius. Both R c and R r demonstrate the rotation period signal with statistical signi?cance by means of the auto-correlation function. In order to determine whether the yearly R ?uctuations within the considered time interval have a periodic component equal to the rotation period, a periodical function, y=p1+p2*sin(2*pi*x/p3+p4), is used to ?t the data of solar radius every year. The correlation coe?cient(cc) between the ?tting data and the original yearly data show that cc are statistically signi?cant in most of considered years. It means that the rotation period signal does clearly exist in R. The result of the correlation analysis between each year’s solar radius and sunspot areas show that all the statistically signi?cant correlation coe?cients are negative, which indicates that the solar radius is anti-phase with sunspot areas. Generally, the correlation coe?cients have obvious statistical signi?cance in the maxima of solar cycles, and their absolute values are larger than these correlation coe?cients of the minima of solar cycles. In the minima of solar cycles, the correlation coe?cients are not statistically signi?cant. This indicates that strong magnetic ?elds have a greater inhibitive e?ect on the radius change than that of weak magnetic ?elds. Surface magnetic ?elds are considered to be channels by which for interior energy can be transferred to the surface, as are convective processes. Magnetic ?elds inhibit convection, causing a decrease of heat transport e?ciency. The strong magnetic ?elds may lead to an increase in magnetic tension force, which would result in compression of the surrounding regions, which, in turn, will shrink the size of the Sun. In the last chapter, a brief summary of this thesis is provided and some unsolved questions about the solar radius are mentioned. And a proposal for future study is made.
Subject Area天文学
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/6628
Collection太阳物理研究组
Affiliation中国科学院云南天文台
Recommended Citation
GB/T 7714
屈智宁. 太阳半径周期分析及物理机制研究[D]. 北京. 中国科学院研究生院,2015.
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