YNAO OpenIR  > 太阳物理研究组
CME活动周统计特征研究
Alternative TitleStatistic Study on Coronal Mass Ejections in Cycle 23
高朋鑫
Subtype硕士
Thesis Advisor李可军
2007-06-08
Degree Grantor中国科学院研究生院(云南天文台)
Place of Conferral北京
Degree Discipline天体物理
Keyword太阳:活动 太阳:日冕物质抛射(cme)
Abstract日冕物质抛射(CME)是大尺度的等离子体和磁场爆发,被认为是引起中等到强烈地磁暴的行星际扰动的主要来源。所以对CME的研究是和空间环境直接相关的重要课题,是近年来太阳物理中一个较为活跃的研究领域。尤其是SOHO/LASCO1996年以来已经观测到了一万多个CME事件,这为CME事件的统计研究提供了空前的机会。本文对CME事件的统计特征的研究均基于SOHO/LASCO的观测数据。作者的工作主要有: 1、分析高低纬CME和黑子数的相位关系,发现高低纬CME都和黑子数同相位;分析CME一个活动周内在日面上的纬度分布发现没有像蝴蝶图那样的纬度迁移。因此我们猜测CME和活动区尺度的活动存在区别。我们知道,黑子是活动区尺度的太阳活动,而CME事件是大尺度的太阳活动,所以猜想不管是黑子还是CME事件都是相应尺度磁场扰动的表现,也就是说,以上结果可能支持CME和大尺度源区磁场结构有关的结论。 2、分析高低纬CME的速度分布发现高低纬速度分布都可以用对数正态分布很好的拟合,并且高低纬速度分布拟合曲线几乎重合,说明相同的非线性驱动机制在对高低纬CME起作用,我们知道太阳高低纬活动区尺度磁场的特点是明显不同的,所以这个结果也应该支持CME和大尺度源区磁场结构有关的结论。但是从统计上来看,如果我们分别把高纬和低纬CME事件看作一个整体,高纬CME事件的速度要比低纬CME事件的速度低。在高纬加速和减速CME的速度分布的对数正态拟合曲线和相应的在低纬加速和减速CME的速度分布的对数正态拟合曲线也有着相似的分布。也就是说在把所有CME事件分为高纬和低纬的情况下,得到的结果仍然是加速和减速CME事件源区没有物理上的差别加强了Yurchyshyn(2005)等人的结果。 3、分析了23周,从1996年9月到2006年6月,CME的纬度和速度分布。在整个活动周内CME发生在所有的纬度范围内,在低纬CME发生的比较频繁,随着纬度的升高CME发生的越来越稀少,这和黑子的纬度分布特点不同。这个结论可能支持CME和大尺度磁场结构有关的结论,甚至是和跨赤道的大尺度磁场结构有关的结论。把CME分为发生在南半球的和北半球的,分别分析其纬度分布规律。从统计上来说,发生在南北半球的CME事件的纬度分布规律是一致的。分析南北半球CME事件个数,发现南半球占优势,证认了Atac和Ozguc(1996)的预测结果和李可军(2002)等人的关于太阳活动的长期时间特征尺度-12个太阳活动周-的预测。分析了发生在南北半球的CME事件的速度分布,两个分布都可以用对数正态分布很好的拟合,并且两条拟合曲线几乎重合,说明相同的非线性驱动机制对南北半球的CME事件起作用。因此我们推断CME的南北半球不对称性可能与太阳内部发动机的不对称作用有关。
Other AbstractCoronal Mass Ejections (CMEs), the large-scale eruptions of plasma and magnetic fields from the Sun, are believed to be the main sources of the strong interplanetary disturbances that cause many moderate to intense geomagnetic storms. So, the study on CMEs is an important topic that relates directly to space environments. Since 1996 January, The Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observator (SOHO) mission has observed the most CMEs, providing us with a great opportunity to examine the properties of CMEs. Based on SOHO/LASCO observation, we study the statistical properties of CMEs. The major results are obtained as follows: 1. We study the phase relation of the sunspot cycle and the coronal mass ejection events respectively at low and high latitudes in detail. We find that the activity of CME events respectively at low and high latitudes all have the same phase as the sunspot activity. We also study the distribution of the CME events from 1996 January to 2005 October on the solar disk. We find that the CME events have no latitudinal drift within a CME cycle. The reason is suggested to be that the sunspots are the activities on the AR scale but the CMEs are that on the large-scale, and they are both the manifestation of magnetic structures destabilized on the corresponding scales. 2.We analyze the distributions of speeds determined for 10513 coronal mass ejections(CMEs) observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliospheric Observatory(SOHO/LASCO) in cycle 23 from 1996 to 2005, respectively at low and high latitudes. The ln(v) distributions of CME events respectively at high and low latitudes are both found to a good approximation they can be fitted with a normal distribution. The fitting curves of the ln(v) distributions for CMEs respectively at high and low latitudes are almost identical, implying that there is statistically no physical distinction between CME events respectively at high and low latitudes, and furnishing evidence to support that CMEs are intrinsically associated with source magnetic structures on a large spatial scale, but CMEs at high latitudes, statistically, are apparently slower than those at low latitudes. Respectively at high and low latitudes, the ln(v) distributions respectively for accelerating and decelerating CME events are nearly identical and also to a good approximation they can be both fitted with a normal distribution. It implies that, statistically, there is no physical distinction between accelerating and decelerating CME events, even if CMEs are divided into those respectively at high and low latitudes, augmenting the results obtained by Yurchyshyn et al.(2005). 3.The latitudinal distribution of Coronal Mass Ejections in Cycle 23, from September 1996 to June 2006, has been analyzed. CMEs occur at all latitudes and are most common at low latitudes. This should furnish evidence to support that CMEs are associated with source magnetic structures on a large spatial scale, even with transequatorial source magnetic structures on a large spatial scale. The latitudinal distributions of CMEs respectively in the northern and southern hemispheres are no difference from the statistical point of view. Through calculating the actual probability of the hemispheric distribution of the activity of the CMEs, we find that a southern dominance of the activity of CMEs is shown to occur in cycles 23 from September 1996 to December 2005, which was predicted by Atac and Ozguc(1996). The conclusion confirms that hypothesis about a 12 cycle periodicity is valid(2002). The speed distributions respectively in the northern and southern hemispheres are to a good approximation they can be fitted with a single lognormal distribution.The speed distributions respectively in the northern and southern hemispheres are no difference from the statistical point of view. This finding implies that, statistically, there is no physical distinction between the CME events in the southern and northern hemispheres, and a same mechanism of a nonlinear nature is acting in both the CME events in the southern and northern hemispheres.
Subject Area天文学
Pages79
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/6597
Collection太阳物理研究组
Recommended Citation
GB/T 7714
高朋鑫. CME活动周统计特征研究[D]. 北京. 中国科学院研究生院(云南天文台),2007.
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