日冕中的活动事件及波动现象
文献类型：学位论文
| 作者 | 薛志科
|
| 学位类别 | 博士 |
| 答辩日期 | 2013-11-28 |
| 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 | 屈中权 |
| 关键词 | 太阳磁场 活动区 暗条 日浪 EUV波 |
| 其他题名 | The Activity Events and Waves in Solar Corona |
| 学位专业 | 天体物理 |
| 中文摘要 | 太阳大气中无时无刻都在发生着剧烈的各种尺度的活动现象，如耀斑、暗条爆发、喷流、日冕物质抛射等等。随着具有高空间分辨率和高时间分辨率的望远镜的投入运行，像太阳与日球天文台（SOHO；Solar and Heliospheric Observatory）、日地关系天文台（STEREO；Solar Terrestrial Relations Observatory）、以及太阳动力学天文台（SDO；Solar Dynamic Observatory），我们能更深入研究细致的太阳结构和短时标的爆发事件，而极紫外(EUV; Extreme Ultraviolet )波的发现和研究就得利于这些望远镜的投入运行。本论文结合两台空间望远镜（STEREO和SDO）观测到的数据，主要分析了与EUV波有关的两个爆发事件，以期待能更深入了解和认识EUV波的特征和本质，以及其它爆发事件（如第四章所述的下落流的动能和热能的转化问题）。我们分析的第一个爆发事件是于2011年9月7日和8日发生在活动区11283里的事件，它包括一系列爆发现象，诸如：暗条爆发，EUV波，暗条振动，暗条物质回落及相关增亮。我们得出的结果是：活动区暗条首先爆发，从而激发了一个EUV波向太阳西北方向传播，当这个EUV波穿过另一个暗条（宁静区暗条）时，引起了这个暗条振动，基于日震学理论，我们估算了振动暗条里的平均磁场强度，大约为18±2 G。一部分等离子体从爆发暗条分离出来并且下落到太阳西北部的区域内，下落流的速度随着高度的减小而逐渐增加，其加速度比太阳重力加速度要小，下落流的特征温度大约为5×10^4 K，当这些等离子团下落到更低层大气中时，高速向下运动的等离子体碰撞低层大气中的等离子体，从而引起了这些等离子体增亮，增亮区域在AIA的8个观测波段都能看到，这表明等离子体的温度分布位于一个很广的范围内，从10^5 K到10^7 K，它同时暗示着动能和热能之间转化过程的发生。我们研究了另一个发生于2011年3月24日的EUV波事件，这个事件中出现了一对连续的EUV波，我们详细研究了它们的拓扑结构和运动学特征。这个事件包含一些引人关注的现象，第一个EUV波首先在一个日浪爆发后出现，在传播过程中，其波前变形和重构非常明显，首先呈现凸形结构，然后变成了线性结构，最后改变为了与最初相反的凹形结构。第一个EUV波的初始速度为947 km/s到560 km/s，当它穿过一个暗条通道时，第一个EUV波减速非常明显，减速后的EUV波传播速度为：430 km/s到312 km/s。随后，第二个EUV波出现在暗条通道的西北边缘，它紧随第一个EUV波向太阳西北方向传播，但是它的波前比较弥散，并且它的传播速度要比第一个EUV波小，只有250 km/s左右。我们推断第一个EUV波的波前形变是由于沿不同传播路径的速度不一样引起的，而它的突然减速暗示着第一个EUV波在遇到暗条通道时发生了折射，同时这个波动事件也提供了一个关于EUV波本质的证据，首先出现的EUV波可能是一个日冕MHD激波，而第二个EUV波可能是由于磁力线被拉伸引起的增亮。通过对这两个太阳活动事件的分析和研究，我们可以看出太阳爆发事件不仅仅与自身的性质有关（如磁能释放），还与周围环境的物理性质有关（如磁场大小，密度等等），我们在研究一个活动事件的同时也可以对周围等离子体的性质进行研究，得到更加全面的结论和理论解释。 |
| 英文摘要 | The acute activity events in the solar atmosphere occur at all times, such as flares, filament eruptions, jets, coronal mass ejections, and so on. With the operation of several telescopes with the high spatial resolution and high temporal resolution, such as Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO), and Solar Dynamic Observatory (SDO), we can study the smaller structures on the Sun and eruptive events with short time-scale in detail. Thanks to these telescopes, we discover and study a lot of Extreme Ultraviolet (EUV) waves. In this paper, using the data observed by STEREO and SDO, we analyze two eruptive events and associated EUV waves to understand their properties and influences and other eruptive events (such as the conversion of kinetic energy and thermal energy of downflows described in Chapter 4).The first eruptive event we study occurred in active region NOAA 11283 on 2011 September 7 and 8, which includes several eruptive phenomena, such as filament eruption, EUV wave, filament oscillation, downflows and brightening. The results are as follows. The active region filament first erupted, and then triggered a EUV wave propagating toward the northwest. When the EUV wave passed through another filament (quiescent filament), it caused the filament to oscillate transversely. Based on coronal seismology, the mean magnetic field strength in the oscillatory filament was estimated to be approximately 18±2 G. Some plasma separated from the filament and fell down to the solar northwest surface after the filament eruption. The velocities of the downflows increased at accelerations lower than the gravitational acceleration. The main characteristic temperature of the downflows was about 5×10^4 K. When the plasma blobs fell down to lower atmospheric heights, the high-speed downward-travelling plasma collided with plasma at lower atmospheric heights, causing the plasma to brighten. The brightening was observed in all 8 AIA channels, demonstrating that the temperature of the plasma in the brightening covered a wide range of values, from 10^5 K to 10^7 K. This brightening indicates the conversion between kinetic energy and thermal energy.We study another EUV wave event on 2011 March 24 in which a pair of consecutive EUV waves took place. We studied the kinematics and morphology of these two EUV waves in detail. This event contains several interesting aspects. The first EUV wave initially appeared after a surge-like eruption. Its front was changed and deformed significantly from a convex shape to a line-shaped appearance, and then to a concave configuration during its propagation to the northwest. The initial speeds ranged from 947 km/s to 560 km/s. The first wave decelerated significantly after it passed through a filament channel. After the deceleration, the final propagation speeds of the wave were from 430 km/s to 312 km/s. The second wave was found to appear after the first wave in the northwest side of the filament channel. Its wave front was more diffused and the speed was around 250 km?s-1, much slower than that of the first wave. The deformation of the first EUV wave was caused by the different speeds along different paths. The sudden deceleration implies that the refraction of the first wave took place at the boundary of the filament channel. The event provides evidence that the first EUV wave may be a coronal MHD shock wave, and the second wave may be the apparent propagation of the brightenings caused by successive stretching of the magnetic field lines.Based on the analysis of these two solar events, we can find that the solar eruptions not only relate to their own nature (such as magnetic energy release) but also to the physical nature of the surrounding environment (e.g. the value of magnetic field, density, and so on). During studying an eruptive event, we can also study the nature of the surrounding plasma, and obtain more comprehensive conclusions and theoretical explanat |
| 学科主题 | 天文学 |
| 语种 | 中文 |
| 页码 | 104 |
| 源URL | [http://ir.ynao.ac.cn/handle/114a53/5123]  |
| 专题 | 云南天文台_光纤阵列太阳光学望远镜研究组 |
| 推荐引用方式 GB/T 7714 | 薛志科. 日冕中的活动事件及波动现象[D]. 北京. 中国科学院研究生院（云南天文台）. 2013. |
入库方式： OAI收割
来源：云南天文台
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