【作者】 徐飞；

【导师】 魏鸣； 李刚；

【作者基本信息】 南京信息工程大学 ， 大气遥感科学与技术， 2017， 博士

【摘要】 太阳风是人类唯一能直接探测到的恒星风,整个地球处于太阳风等离子体不断的吹拂中,几乎所有对地球影响的事件都通过太阳风等离子体作为媒介来传递,所以深入理解太阳风等离子体,对其正确的分类和认知、深入了解其各种特性对所有和太阳风等离子体相关的研究都有着重要的意义。本文发展了一种全新的即不依赖于重离子数据、也不需要太阳风历史数据和激波发生时间的太阳风等离子体分类方案;在新分类方案基础上分析了 1AU处不同太阳风等离子体各种性质的统计特征,深入认识了四种太阳风的性质特点;分析了 1AU处太阳风磁场矢量的角度分布函数,分析其对太阳周的依赖性及其它特点和应用。首先,本文介绍了现有几种太阳风等离子体分类方法的优点和不足,根据对太阳风的认识和经验,搜集、创建了 15个已知太阳风的列表,针对这些列表,利用OMINI2数据,考查了9个太阳风等离子体参数,最终选取了最佳的太阳风列表和最佳的参数组合,发展出了一种全新的等离子体分类方案,此方案只需要3个等离子体参数,即:太阳风质子的比熵Sp= Tp/np2/3;太阳风(质子)的阿芬速度VA = B/(47πmpnp)1/2;与太阳风速度相关的太阳风的预期温度Texp=(Vsw/258)3.113和实际测量太阳风(质子)温度的比值Texp/Tp。为了计算这三个参数,需要测量太阳风四个最基本的物理量:质子数密度np;质子温度Tp;磁场强度B和太阳风速度Vsw。该方案能够将太阳风分成四种等离子体:冕洞起源的等离子体(Coronal Hole Origin Plasma,简写为CHOP);冕流带起源等离子体(Streamer Belt Origin Plasma,简写为SBOP);磁场扇区极性反转区域起源的等离子体(Sector-Reversal-Region Plasma,简写为SRRP);源自日冕物质抛射的等离子体(Ejecta)。通过对比其他分类方法、用其它已知列表交叉检验,显示新的分类方案准确度高,分类结果科学可靠。其次,使用全新的分类方案,深入研究了 1AU处的太阳风等离子体的多个性质,并发现了新的物理问题:速度非常高的太阳风大部分是Ejecta;低马赫数的太阳风大部分是Ejecta,高马赫数的太阳风大部分是SRRP;磁场方向垂直于帕克螺旋线的太阳风大部分是SBOP(太阳活动极小年)或Ejecta(太阳活动极大年);磁场方向长时间沿径向的太阳风大部分是SRRP;磁场方向指出黄道面的太阳风大部分是Ejecta(太阳活动极大年)或SRRP(太阳活动极小年);由C6+/C5+～O7+/O6+关系可知,CHOP和SBOP有相似的发生机制,Ejecta和SRRP有相似的发生机制,为什么会有这样的相似性,值得进一步研究。最后,本文对1AU处的太阳风磁场角度分布做了研究。发现在一个很宽的α角度范围内,磁场的角度分布函数f(α)的拟合结果显示分布函数有两个主要部分,一个在小角度,一个在大角度。其中大角度的成分可以近似看作一个指数衰减成分,这可能是太阳风中的电流片存在而造成的。本文的分析表明,1AU处的太阳风磁场角度分布函数f(α)特别是f(α)的第二个成分,是具有太阳周期依赖的,这表明第二个成分取决于太阳风的类型;f(α)的另一个重要特征是α2的时间尺度特性:在大范围的时间尺度τ上,α2与τ成线性关系。这为太阳风湍流MHD模型提供了一个约束,相关的理论模型都可以参考这个基于观测的时间尺度特性,用来检验模型的合理性。综上所述,本文提出的新的等离子体分类方案科学可靠,仅仅需要测量四个最基本太阳风等离子体物理量,对比其它分类方法有着方便、快速、准确率高的优点,且新分类并认识了一种磁场扇区极性反转区域产生的等离子体。通过对1AU处的太阳风等离子体的性质和磁场角度分布研究,加深了对太阳风等离子体的认识,获得太阳风磁场角度分布函数,为相关理论模型提供了一个基于观测事实的约束条件。更多还原

【Abstract】 Solar wind is the only star wind that human can directly detect.The whole earth is in the constantly blowing of solar wind plasma.Almost all of the Earth’s events through the solar wind plasma as a medium to pass,so in-depth understanding of the solar wind plasma,its correct Classification and cognition,in-depth understanding of its various characteristics of all solar and solar plasma-related research are of great significance.In this paper,a new solar wind plasma categorization scheme,which does not depend on heavy ion data and does not require solar wind history data and shock time,is developed.Based on the new categorization scheme,the effects of different solar wind plasma and the characteristics of the four kinds of solar winds are deeply studied.The angular distribution function of solar wind magnetic field vector at 1AU is analyzed,and its dependence on solar cycle and other characteristics and applications are discussed.Firstly,this paper introduces the advantages and disadvantages of several solar wind plasma classification methods.Based on the knowledge and experience of solar wind,a list of 15 known solar winds is collected.For these lists,OMINI2 data are used to examine 9 solar wind plasma parameters,the final selection of the best solar wind list and the best combination of parameters,the development of a new plasma classification program,this program requires only three plasma parameters,namely:solar wind proton specific entropy Sp=Tp/np2/3 and the expected temperature of the solar wind associated with the solar wind speed Texp =(Vsw/258)3.113 and the actual measurement of the solar wind(Proton)temperature ratio Texp/Tp.In order to calculate these three parameters,it is necessary to measure the four most fundamental physical quantities of the solar wind:proton number density np;proton temperature Tp;magnetic field strength B and solar wind velocity Vsw.The scheme is capable of dividing the solar wind into four kinds of plasmas:Coronal Hole Origin Plasma(abbreviated as CHOP);Streamer Belt Origin Plasma(abbreviated as SBOP);Sector-Reversal-Region Plasma(abbreviated as SRRP);and plasma derived from coronal mass ejections(Ejecta).By comparing the other classification methods,using other known list cross test,show the new classification program is highly accurate,the classification results are scientific and reliable.Secondly,By using the new classification scheme,in-depth study of the solar wind plasma of the many properties at 1AU and found a new physical problem:very high speed solar wind is Ejecta;low Mach number of solar wind is mostly Ejecta,Most of the solar winds of the high Mach number are SRRP;When the magnetic field direction is perpendicular to the Parker spiral,most of the solar wind is SBOP(solar activity minimalist)or Ejecta(solar activity is great).When solar wind magnetic field long time along the radial direction,the plasma mostly are SRRP.When the solar wind magnetic field point out of the ecliptic plane,the plasma is mostly Ejecta at solar maximum,or is mostly SRRP at solar minimum.From C6+/C5+～O7+/O6+ relationship,one can find out CHOP and SBOP have similar occurrences Mechanism,Ejecta and SRRP have a similar mechanism,why is there such a similarity,worthy of further study.Finally,the angle distribution of the solar wind field at 1AU is studied in this paper.Found in a wide angle range,the fitting of the angular distribution function f(α)of the magnetic field shows that the distribution function has two main components,one at a small angle and one at a large angle.The large angle of the composition can be expressed as an exponential decay component,which may be caused by the presence of current sheets in the solar wind.The analysis of this paper shows that the solar wind magnetic field angular distribution function at 1AU,especially the second component has a solar cycle dependence,which indicates that the second component could depends on the type of solar wind;another important feature is the time scale dependence:On a wide range of time scales,with a linear relationship.This provides a constraint for the solar wind MHD turbulence model.The relevant theoretical model can refer to this observation-based time-scale characteristic to test the rationality of the model.In summary,the new plasma categorization scheme proposed in this paper is scientific and reliable,only need to measure the four fundamental solar wind plasma physical quantity,compared with other classification methods this new one is convenient,fast,and with high accuracy.With this new classification one can recognize and understand a new kind of solar wind plasma,Sector-Reversal-Region Plasma.Based on the study of the properties of solar wind plasma and the angular distribution of magnetic field at 1AU,the knowledge of solar wind plasma is deepened and the angle distribution function of solar wind field is obtained,which provides a constraint condition based on observation fact.更多还原