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题名:
太阳爆发理论和模型在高能天体物理研究中的应用
其他题名: Applications of Solar Eruption Theory and Model to Studies in High-Energy Astrophysics
作者: 蒙盈
学位类别: 博士
学位专业: 天体物理
学位授予日期: 2014-05-24
授予单位: 中国科学院研究生院(云南天文台)
授予地点: 北京
导师: 林隽
学科分类: 天文学
关键词: 不稳定性 ; MHD ; 磁重联 ; 中子星 ; 喷流
中文摘要: 日冕物质抛射是太阳表面的一种爆发现象,它可以使磁通量绳和磁化等离 子体快速地抛射到外层日冕。在这个过程中巨大的磁场能量迅速释放,并转化 为其他形式的能量。人们通常认为它的驱动机制主要为磁结构的灾变和磁重 联。由于太阳是离地球最近的,而且是对人类最重要的一颗恒星,太阳物理, 特别是对人类生活有重要影响的太阳爆发活动的研究得到了深入的发展。 在高能天体物理领域中,也存在着与日冕物质抛射相类似的物理现象。例 如,磁中子星的大耀发以及黑洞吸积盘系统产生的间歇性喷流等,这些都是系 统在短时间内释放大量的磁能并抛射物质的过程,而这些过程的具体细节还不 被人们所知。因此,运用太阳爆发的相应理论和模型来对这些未知的活动进行 研究,具有重要的借鉴作用。 软伽马射线复现源被认为是磁中子星的一种,发生在软伽马射线复现源中 的大耀发在短时标内释放出巨大的能量。驱动这些爆发的能量来源与于贮存在 磁中子星磁球层内的磁场能量,而触发和驱动机制则为磁场结构的灾变不稳定 性和磁重联。参考太阳日冕物质抛射的理论和模型,我们发展了一个解析的理 论模型来解释磁中子星的大耀发。在这个模型中,壳层的转动和错位造成磁场 的扭曲和变形,导致磁通量绳在磁球层中形成以及能量在相应的磁场位形中 积累。当储存在磁场结构中的能量和螺度达到了阈值,系统就会失去平衡,磁 通量绳被以灾变的方式向外抛射,而磁重联使灾变演化成真正的爆发。以SGR 1806-20为例,我们计算了在这样一次爆发过程中所释放出的磁自由能(即系 统的总磁能和相应势场能量之差)大于10^47 尔格,足以驱动一次大耀发。释放 的磁自由能被转化为辐射能、磁通量绳的动能和引力势能。我们还计算了SGR 1806 - 20 、SGR 0526-66 和SGR 1900+14 这三次大耀发过程的光变曲线并将他 们与观测数据相比较。我们计算得出的光变曲线能很好地与观测数据符合。 在许多天体物理中的黑洞吸积盘系统中,由等离子体团构成的间歇性喷流 已经被观测到,但是他们的起源还不清楚。以Yuan 等人的模型为基础,我们 发展了一个考虑了相对论效应的磁流体动力学模型来解释黑洞吸积盘系统中的 间歇性喷流。我们以Sgr A* 和恒星级黑洞为例子,研究等间歇性喷流离子体团 的动力学特征。我们的模型结果表明,等离子体团被抛射出去后,可以在短时 间内获得很大的洛仑兹因子,并且不断地发生膨胀。然后,我们进一步地研究 了相继抛射的等离子体团间的碰撞,发现恒星级黑洞产生的等离子体团之间可 以发生碰撞,而单个等离子体团所携带的磁能大于10^50 尔格。在两个等离子体 团的相互碰撞过程中,通过磁重联可将大约一半的磁场能量释放出来,因此这 些等离子体团的碰撞能够产生一次伽玛暴。
英文摘要: Coronal mass ejection(CME) is a phenomenon of solar eruption, it causes the flux rope and magnetized plasma to be thrusted outward. In this process, huge magnetic energy is rapidly released and converted to other forms of energy. It is believed that catastrophe and magnetic reconnection trigger the CME. Because the sun is closest to the earth and play an important role in human life, the solar physics has further development. In the field of high energy astrophysics, there are some physical phenomena have the operation of a common physical mechanism with solar CME (e.g. magnetar giant flares and episodic jets from black hole and accretion disk systems). Huge magnetic energy is released and plasmoid is ejected from the system in this process, and the details are still unknown. Therefore, applications of the solar cme model to the phenomena in the high-energy astrophysics are very meaningful. Giant flares on soft gamma-ray repeaters that are thought to take place on magnetars release enormous energy in a short time interval. Their power can be explained by catastrophic instabilities occurring in the magnetic field configuration and the subsequent magnetic reconnection. By analogy with the coronal mass ejection (CME) events on the Sun, we develop a theoretical model via an analytic approach for magnetar giant flares. In this model, the rotation and/or displacement of the crust causes the field to twist and deform, leading to flux rope formation in the magnetosphere and energy accumulation in the related configuration. When the energy and helicity stored in the configuration reach a threshold, the system loses its equilibrium, the flux rope is ejected outward in a catastrophic way, and magnetic reconnection helps the catastrophe develop to a plausible eruption. By taking SGR 1806 - 20 as an example, we calculate the free magnetic energy released in such an eruptive process and find that it is more than 10^47 ergs, which is enough to power a giant flare. The released free magnetic energy is converted into radiative energy, kinetic energy and gravitational energy of the flux rope. We calculated the light curves of the eruptive processes for the giant flares of SGR 1806 - 20, SGR 0526-66 and SGR 1900+14, and compared them with the observational data. The calculated light curves are in good agreement with the observed light curves of giant flares. In many astrophysical black hole systems, episodic jets of plasma blobs have been observed, although the origin of the episodic ejection of blobs is unclear. Base on the model proposed by Yuan et al., we develop an magnetohydrodynamical model for episodic ejections of the plasma blob from black hole and accretion disk systems, considering the relativistic effect. By taking Sgr A* and the stellar size black hole for examples, we study the dynamics of the plasma blob. Our model results show that the blobs can attain large Lorentz factor quickly and undergo expansion after thrusting outward. And we further study the collision between two consecutive ejections in our model, and find the consecutive plasma blobs from the stellar size black hole can collide with each other and each of them has magnetic energy of more than 10^50 ergs in our calculation. In the this collision, about half the magnetic energy is released by magnetic reconnection, so multiple collisions among several such blobs can power a Gamma-ray burst.
语种: 中文
总页数: 90
内容类型: 学位论文
URI标识: http://ir.ynao.ac.cn/handle/114a53/6625
Appears in Collections:太阳物理研究组_学位论文

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