日冕磁绳的灾变及相关现象研究

发布时间：2018-08-08 13:59

【摘要】：太阳大尺度爆发活动是日地空间活动的主要扰动源,主要包括日珥(暗条)爆发、耀斑和日冕物质抛射等现象。这些爆发活动彼此之间并非独立,它们通常被认为是同一个日冕磁绳爆发活动在不同的时间范围和空间区域内的具体表现形式。研究日冕磁绳爆发的现象和机制,对于理解这些爆发现象的物理过程,促进空间天气预报的发展有重要意义。本文主要研究的是日冕磁绳爆发的灾变驱动机制,以及与之相关的观测现象的分析。首先,我们利用数值模拟的方法,研究了日冕磁绳系统的灾变特性,包括不同光球层磁通分布下系统灾变演化特性的差异,以及日冕磁绳系统中存在的不同类型的灾变现象等等;然后,我们研究了卫星观测到的一个典型的太阳爆发活动事件,分析了其中的动力学演化过程,以及爆发活动的驱动机制,并在此基础上,与数值模拟中的得到的磁绳的灾变演化特性进行对比分析,从而对这个爆发活动的演化过程给出一个系统完整的描述;此外,我们还研究了太阳爆发活动所驱动的波和振动现象,利用振动参数,估算局地物理参数并分析波的相关物理性质。1.日冕磁绳系统的灾变特性在现有的观测条件下,日冕中的磁场位形无法直接测量,只有光球层的磁通分布可以直接观测到。因此我们尝试利用数值模拟,研究光球层磁场条件与日冕磁绳系统灾变特性之间的关系,以期能够为太阳爆发活动的预报工作给出理论上的依据。通过计算发现,系统的向上灾变特性与光球层磁通分布有着密切的联系:如果光球层活动区的正负极性靠得过近,或是正负极性对应的源区过弱,都会造成磁绳系统中不会发生向上灾变,即在这种光球层磁通分布下,磁绳系统不会爆发。我们对部分开放场和全闭合背景场的情况都进行了计算分析,发现磁绳系统均满足类似的结论,这表明背景场的开放性不是决定系统是否存在灾变的唯一因素,任何会改变背景场位形的参数都有可能影响系统的灾变特性。同时,通过详细分析有灾变的情况,我们还发现灾变演化过程的激烈程度同样受光球层磁场条件的影响:正负极性距离越大,源区越强,系统的演化过程越激烈,即磁绳系统的活动性越强。在以往的研究中,分析的都是向上灾变的演化过程。通过数值模拟计算,我们发现,除了以往被广泛研究的向上灾变以外,日冕磁绳系统中还存在一个磁绳向下运动的灾变,被称为向下灾变。向下灾变的过程中,即使系统中不存在磁场重联,磁能同样会被释放。在这种情况下,系统主要通过洛伦兹力的做功来释放磁能,且其量级与太阳爆发事件释放能量的典型值相当。因此,洛伦兹力在灾变中起到了重要的作用。在此基础上,我们进一步研究了光球层磁通分布对向下灾变的影响,结果发现了类似的结果..只有当磁通分布满足特定条件,系统中才会发生向下灾变。值得注意的是,在研究中发现,向上灾变和向下灾变总是伴随出现,即系统存在向上灾变或是向下灾变时,需要满足光球层磁通分布相同。2.通量注入过程引起爆发活动现象的观测分析通过对一个爆发日珥事件的观测分析,我们发现在日珥爆发之前的两天时间内,发生了至少三次通量注入过程:来自色球层的纤维状物质上浮,与上方的日珥相互作用并最终融合在一起。这种通量注入过程会通过色球纤维结构向日珥中注入磁通量,从而引起日珥缓慢抬升速度的明显增加,并最终爆发形成日冕物质抛射。通过分析外部磁场随高度的衰减,我们发现正是由于通量注入过程,使得日珥上升到外部磁场衰减足够快的高度,于是系统发生了 torus不稳定性从而导致了日珥的爆发。因此,通量注入过程就是这个日珥爆发事件的驱动原因。通过与数值模拟中得到的日冕磁绳系统灾变演化特性的对比分析,我们发现,正是通量注入过程不断的将磁通量注入了日珥所在的磁绳系统,使得系统逐渐演化到所对应的灾变点,于是系统失衡产生灾变。由于灾变点恰好就是torus不稳定性发生的临界状态,因此灾变的具体演化过程表现为torus不稳定性。3.太阳爆发活动产生的波和振动现象的分析太阳的爆发活动还会引起许多其他的观测现象。我们研究了一个大尺度EUV波事件,它是由一个耀斑产生的日冕物质抛射所驱动的。EUV波在传播的过程中,与传播路径上的冕环和日珥相互作用,驱动冕环和日珥开始振动。通过分析观测数据,我们得到了冕环和日珥的相关物理参数。利用这些参数,我们估算了太阳表面振动结构所处区域的局地物理参数。同时,结合冕环和日珥的空间位置信息,我们还估算了 EUV波的传播高度以及波的总能量。
[Abstract]:The solar large-scale eruption is the main disturbance source of the solar terrestrial space activities, mainly including the eruptions of prominence (dark strips), flares and coronal mass ejections. These eruptions are not independent of each other. They are usually considered to be the specific manifestations of the same coronal magnetic rope eruption in the different time range and space area. The study of the phenomenon and mechanism of the coronal magnetic rope burst is of great significance for understanding the physical process of these eruptions and promoting the development of the space weather forecast. This paper mainly deals with the catastrophic driving mechanism of the coronal magnetic rope burst and the analysis of the observed phenomena related to it. First, we have studied the method of numerical simulation. The catastrophic characteristics of the coronal magnetic rope system include the difference in the characteristics of the system catastrophe and the different types of catastrophic phenomena in the coronal magnetic rope system, as well as the different types of catastrophes in the coronal magnetic rope system, and so on. Then, we have studied a typical solar explosion event observed by the satellite, and analyzed its dynamic evolution process. And on this basis, and on this basis, compared with the characteristics of the catastrophic evolution of the magnetic cord in the numerical simulation, a systematic and complete description of the evolution process of the eruption activity is given. In addition, we also study the wave and vibration phenomena driven by the solar explosion, and use the vibration parameters to estimate. The local physical parameters and the analysis of the related physical properties of the wave.1. coronal magnetic rope system, the characteristics of the coronal magnetic rope system can not be measured directly in the current corona, only the magnetic flux distribution in the sphere can be observed directly. Therefore, we try to use the numerical simulation to study the magnetic field conditions of the sphere and the coronal magnetic rope system. The relationship between the characteristics of the catastrophe is expected to provide a theoretical basis for the prediction of the solar eruption. It is found that the upward catastrophic characteristics of the system are closely related to the flux distribution of the photosphere: if the positive and negative polarity of the sphere of the sphere is too close, or the source area corresponding to the positive and negative polarity is too weak, it will all be caused. There will not be an upward catastrophe in the magnetic rope system, that is, the magnetic rope system will not break out under the flux distribution of the sphere layer. We have calculated and analyzed the conditions of the partial open field and the fully closed background field. It is found that the magnetic rope system satisfies the similar conclusion, which indicates that the opening of the background field is not the only one to determine whether the system has a catastrophe or not. At the same time, we also find that the severity of the catastrophic process is also affected by the magnetic field conditions of the photosphere: the greater the distance between the positive and negative polarity, the stronger the source area, the more intense the evolution of the system, the magnetic rope system. The more active the system is. In previous studies, the analysis is the evolutionary process of the upward catastrophe. Through numerical simulation, we find that there is a magnetic rope downward movement in the coronal rope system besides the previously widely studied upward catastrophes, which is called downward catastrophe. In the process of downward catastrophe, even the system is in the process. There is no magnetic reconnection, and the magnetic energy is also released. In this case, the system releases the magnetic energy mainly through the work of the Lorenz force, and its magnitude is equivalent to the typical value of the energy released by the solar eruption event. Therefore, Lorenz force plays an important role in the catastrophe. On this basis, we further study the magnetic flux of the photosphere. The effect of distribution on the downward catastrophe has been found. The downward catastrophe occurs only when the flux distribution satisfies specific conditions. It is noted that in the study, it is found that the upward and downward catastrophes always accompany the system, that is, the system needs to meet the flux of the photosphere when there is a catastrophic or downward catastrophe. Observation and analysis of the phenomenon of explosive activity caused by the same.2. flux injection process, we found that at least three times of flux injection process in two days before the prominence eruption: the fibrous material from the chromosphere layer, interacting with the prominence above and finally fusion. Together, the flux injection process will inject magnetic flux into the solar prominence through the structure of the chromosphere, causing a significant increase in the slow lifting speed of the prominence and eventually forming a coronal mass ejection. By analyzing the attenuation of the external magnetic field with the height, we find that the prominence is rising to the external magnetic flux because of the flux injection process. The field attenuates a high enough height, so the system has torus instability which leads to the eruption of the prominence. Therefore, the flux injection process is the driving cause of the event of the prominence. By the comparison of the catastrophic characteristics of the coronal cord system obtained in the numerical simulation, we find that it is the flux injection process. The magnetic flux is injected into the magnetic rope system where the prominence is located, so that the system gradually evolves to the corresponding catastrophe, so the system imbalance produces the catastrophe. Because the catastrophic point is the critical state of the torus instability, the concrete evolution of the catastrophe is manifested by the waves and vibrations produced by the torus instability.3. solar explosion. The phenomenal analysis of the solar explosion will also cause many other observational phenomena. We have studied a large scale EUV wave event, which is a.EUV wave driven by a coronal mass ejection produced by a flare, interacting with the coronal rings and prominences on the propagation path, driving the vibration of the coronal rings and prominences. By analyzing the observation data, we get the physical parameters of the coronal ring and prominence. By using these parameters, we estimate the local physical parameters in the region of the vibration structure of the solar surface. At the same time, we also estimate the propagation height of the EUV wave and the total energy of the wave in conjunction with the spatial position information of the coronal ring and the prominence.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P182.62

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