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利用SDO高时空分辨率资料对小尺度日冕极紫外波的观测研究
Alternative TitleThe observational study on small-scale extreme ultraviolet waves with high temporal and spacial resolution data from the SDO
郑瑞生
Subtype博士
Thesis Advisor姜云春 ; 李可军
2012-05-28
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 极紫外波 日冕物质抛射 暗条
Abstract日冕(corona)极紫外(EUV)波是在日冕里传播的大尺度明亮波前,与日冕物质抛射(CME)有着密切的联系。第一个EUV波是用搭载在太阳与日球天文台(SOHO;Solar and Heliospheric Observatory)上的极紫外成像望远镜(EIT;EUV Imaging Telescope)观测得到的,所以一开始称为“EIT波”。尽管已经被详细研究了15年,但是对EUV波的理解还不是很清楚,仍然有很多未解决的问题,尤其是EUV波的物理本质和触发机制。太阳动力天文台(SDO;Solar Dynamic Observatory)的上天,提供了高时空分辨率的观测资料,使得系统详细地分析研究EUV波成为可能。这里,结合日地关系天文台(STEREO;Solar Terrestrial Relations Observatory)和SDO上EUV波段的观测资料,我们详细分析了几个特殊的EUV波,尝试着去分析EUV波的物理本质和起源问题。另外,我们挑选的主要是一些小尺度(small-scale)EUV波,试图获得不同尺度的EUV波之间的联系和区别。 2010年12月1日,SDO观测到一个小尺度EUV波在日面中心附近爆发,伴随着一个相应的迷你CME(mini-CME)。这个CME显示出典型CME的所有低日冕特征,是由一个小暗条(filament)的爆发引起的。这个暗条长度约为30'',是典型的迷你暗条(mini-filament)。尽管爆发非常微弱,但是EUV波有一个几乎半圆形的波前,并以相同的速度(220-250km/s)向外传播,而且有很小的角度相关性。CME的横向扩张是非对称的,倾向于朝北边运动,CME环的南部足点几乎没有移动。横向扩张导致了长持续时间的(long-duration)强暗区(dimming),反映出CME的范围。对比CME的起动时刻和初始速度,EUV波很可能是由CME环的快速膨胀触发的。我们的分析证明这个小尺度EUV波是真正的波,可以用快模(fast-mode)磁流体动力(MHD)波来解释。 利用SDO的高时间和空间分辨率资料,我们展示了在2010年11月11日三个小时之内连续发生的四个相似(homologous)EUV波。所有的EUV波都源于相同的的磁流浮现区域(EFR),都在相同的方向传播,都伴随着日浪(surge)、微弱的耀斑(flare)和模糊的CME,而且在SDO所有的EUV波段里都有着基本相同的外形。这些波以280-500km s$^{-1}$的均匀速度传播,有着很小的角度相关性,意味着这些相似EUV波很可能可以解释为快模MHD波。这些EUV波很可能涉及不止一个的驱动机制,最可能的是被日浪驱动,由于它们之间紧密的时间和位置关系。我们也认为这些相似EUV波紧密关联着浮现区磁流的持续浮现和对消,这可以为连续EUV波的开始和触发提供足够的能量。 利用SDO的高时间和空间分辨率资料,我们展示了发生在2010年3月1日的一个与失败暗条爆发相关的EUV波,这个事件中没有相应的CME产生。结合(photosphere)、色球(chromosphere)和日冕的高质量的资料,我们研究了EUV波的特征以及波与相应爆发间的关系。事件发生在一个小活动区附近的短暂区域(ephemeral region),这个区域里持续的磁流对消产生了爆发前增亮和两个EUV喷流(jet),并激活了暗条爆发,伴随着一个微耀斑(microflare)。在爆发之后,暗条物质出现在远离爆发中心的地方,周围的冕环看起来并没有受影响。 很明显这个暗条爆发失败了,也没有产生相应的CME。EUV波就发生在北边喷流到达之后,而且看起来像是源于这个喷流的前面,而不是爆发中心。EUV波接近匀速地传播,速度范围为260-350km/s,在后期有轻微的负加速度。值得注意的是,EUV波碰到一簇冕环后,继续向前传播,而冕环基本上不受影响。我们的分析证明这个EUV波是个真正的波,可以解释为一个快模MHD波。另外,EUV波和喷流在时间和空间上的紧密关系,提供了当CME没有发生的时候EUV波可能由喷流触发的证据。 快速日冕EUV波(速度>1000km/s)是非常罕见的。利用SDO的高时空分辨率资料,我们研究了一个发生在2011年9月30日的快速EUV波,联系着一个迷你暗条爆发、一个C1.0耀斑和一个CME。这个事件发生在两个活动区之间的边缘区域,迷你暗条快速地爆发,看起来像爆裂喷流(blowout jet)一样,伴随着耀斑和CME。CME的前锋很有可能是由覆盖在上方的大尺度冕环直接演化而来的。EUV波的起始时间与喷流和耀斑的初始时刻几乎是同时的。EUV波的起点远离耀斑中心,与快速喷流有着紧密的位置关系。EUV波有着大约1100km/s的初始速度,在后期还有轻微的减速,速度降到500km/s左右。EUV波在很小的角度范围内传播,很有可能是想要避开两边的活动区。所有的结果都证明这个快速EUV波是个快模MHD波。因为CME打开了大尺度的环,它的前锋很有可能在EUV波波前产生之后形成,所以EUV波不可能被CME驱动。EUV波最有可能是被喷流触发的,因为两者之间有着紧密的时间和位置关系。
Other Abstract``Extreme Ultraviolet (EUV) waves'' are propagating large-scale wavelike bright transients in the corona, strongly associated with coronal mass ejections (CMEs). The first EUV wave was discovered by the EUV Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) spacecraft, thus they are originally named ``EIT waves''. Though studied in detailed for almost 15 years, the understanding for EUV waves is still not very clear, and there are many unresolved problems, especially that on the physical nature and driving mechanism of EUV waves. Since the launch of the Solar Dynamic Observatory (SDO), its high temporal and spatial resolution observations make it possible to study EUV waves in detail. Here, combining with the observations from the SDO and the Solar Terrestrial Relations Observatory (STEREO), we studied some special EUV waves, trying to analysis the nature and origin for EUV waves. Moreover, we mainly chose the small-scale EUV waves, and want to get their relations and differences with the large-scale ones. The main results are as follows. We present a possible detection of a fast-mode EUV wave associated with a mini-CME observed by the SDO. On 2010 December 1, a small-scale EUV wave erupted near the disk center associated with a mini-CME, which showed all the low corona manifestations of a typical CME. The CME was triggered by the eruption of a mini-filament, with a typical length of about 30''. Although the eruption was tiny, the wave had the appearance of an almost semicircular front and propagated at a uniform velocity of 220--250 km/s with very little angular dependence. The CME lateral expansion was asymmetric with an inclination toward north, and the southern footprints of the CME loops hardly shifted. The lateral expansion resulted in deep long-duration dimmings, showing the CME extent. Comparing the onset and the initial speed of the CME, the wave was likely triggered by the rapid expansion of the CME loops. Our analysis confirms that the small-scale EUV wave is a true wave, interpreted as the fast-mode MHD wave. Taking advantage of the high temporal and spatial resolution of the SDO observations, we present four homologous EUV waves within 3 hours on 2010 November 11. All EUV waves emanated from the same emerging flux region (EFR), propagated into the same directions, and were accompanied by surges, weak flares and faint CMEs. The waves had the basically same appearance in all EUV wavebands of the Atmospheric Imaging Assembly on the SDO. The waves propagated at constant velocities in the range of 280-500 km/s, with little angular dependence, which indicated that the homologous waves could be likely interpreted as fast-mode waves. The waves are supposed to likely involve more than one driving mechanism, and it was most probable that the waves were driven by the surges, due to their close timing and location relations. We also propose that the homologous waves were intimately associated with the continuous emergence and cancelation of magnetic flux in the EFR, which could supply sufficient energy and trigger the onsets of the waves. Taking advantage of the high temporal and spatial resolution of the SDO observations, we present an EUV wave associated with a failed filament eruption that generated no CME on 2011 March 1. We aim at understanding the nature and origin of this EUV wave. Combining the high-quality observations in the photosphere, the chromosphere, and the corona, we studied the characteristics of the wave and its relations to the associated eruption. The event occurred at an ephemeral region near a small active region. The continuous magnetic flux cancelation in the ephemeral region produced pre-eruption brightenings and two EUV jets, and excited the filament eruption, accompanying it with a microflare. After the eruption, the filament material appeared far from the eruption center, and the ambient loops seemed to be intact. It was evident that the filament eruption had failed and was not associated with a CME. The wave happened just after the north jet arrived, and apparently emanated ahead of the north jet, far from the eruption center. The wave propagated at nearly constant velocities in the range of 260-350 km/s, with a slight negative acceleration in the last phase. Remarkably, the wave continued to propagate, and a loop in its passage was intact when the wave and the loop met. Our analysis confirms that the EUV wave is a true wave, which we interpret as a fast-mode wave. In addition, the close temporal and spatial relationship between the wave and the jet provides evidence that the wave was likely triggered by the jet when the CME failed to happen. The fast EUV waves (>1000 km/s) in the solar corona were very rare in the past. Taking advantage of the high temporal and spatial resolution of the SDO observations, we present a fast EUV wave associated with a mini-filament eruption, a C1.0 flare, and a CME on 2011 September 30. The event took place at the periphery between two active regions (ARs). The mini-filament rapidly erupted as a blowout jet, associated with a flare and a CME. The CME front was likely developed from the large-scale overlying loops. The wave onset was nearly simultaneous with the start of the jet and the flare. The wave departed far from the flare center, and showed a closely location relation with the rapid jet. The wave had a initial speed of about 1100 km/s and a slight deceleration in the last phase, and the velocity decreased to about 500 km/s. The wave propagated in a narrow angle extent, likely because it wanted to avoid the ARs on both sides. All the results provide evidence that the fast EUV wave was a fast-mode MHD wave. The wave did not like to be driven the CME, because it opened up the large-scale loops and its front likely formed later than the wave. The wave was most likely triggered by the jet, due to their close timing and location relations.
Subject Area天文学
Pages142
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/6616
Collection太阳物理研究组
Recommended Citation
GB/T 7714
郑瑞生. 利用SDO高时空分辨率资料对小尺度日冕极紫外波的观测研究[D]. 北京. 中国科学院研究生院(云南天文台),2012.
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