| 其他摘要 | Global EUV waves are spectacular traveling disturbances in the solar corona associated with energetic eruptions such as (CMEs) and flares. Since the EIT telescope observed coronal waves in 1998, the origin of single, diffuse coronal waves has been the subject of considerable controversy. Some scholars believe that coronal waves are driven by CMEs, while others believe they are excited by flares. Recently, the high spatio-temporal imaging observation taken from AIA/SDO indicates that some coronal waves compose of multiple wavefronts, which brings new challenges for explaining the origin of the coronal waves. Therefore, it is essential to investigate the coronal wave further and provide observational evidence for the coronal waves’ physical nature and generation mechanism. The oscillations of the filaments, the cavities, and the coronal loops driven by the interactions of the coronal waves could be used to diagnose these coronal structures’ magnetic field strength using corona seismology, especially in the absence of direct approaches. The study of coronal waves is significant in diagnosing their physical essence, excitation mechanism, and energy transport. In this paper, the generation mechanism, physical essence, propagation characteristics, and interaction with coronal structures (such as CH) of QFP wave train with multiple wavefronts are studied by using AIA/SDO high spatio-temperal resolution imaging data and EUVI/STEREO multiangle observation.Generally, the large-scale EUV waves, narrow QFP wave trains, and broad QFP wave trains are observed separately. In Chapter 3, we report an eruption event that occurred at the west limb of the solar disk on 2013 April 23, simultaneously observing these three types of waves, which provide important observational data for comparing the physical parameter among them. Since the eruption origin was located at the west limb of the solar disk, the decoupling process between the large-scale EUV wave and the CME bubble can be clearly identified in the running-difference images. The composition propagating on the solar surface of the large-scale EUV wave interacted with a remote coronal loops system and reflected from the collision site. Another loop system captured a partial wavefront and constrained it to propagate along the loops system. It is worth noting that the mode conversion should occur during this process because the wave first propagated perpendicular to the direction of magnetic field lines and then along the magnetic field lines after the loops system constrained it. As mentioned above, the large-scale EUV waves are generally propagating ahead of the CME bubble. However, a broad QFP wave train was observed propagating inside the CME bubble, which emanated after the CME bubble was complete formation. Combined with the temporal and spatial relationship between the CME and broad QFP wave train, it is hard to explain the origin of this broad wave train using the CME lateral expansion. Except for the above two types of coronal waves, a narrow QFP wave train propagating along the closed coronal loops was also be observed. We investigated and compared the physical parameters of these three types of coronal waves, such as generation mechanism, speed and periodicity, and energy flux. Based on the obtained physical parameters, we further estimated the magnetic field strength of the corona and coronal loops.The corona has regions with large density and temperature sudden variations (e.g., CHs, ARs). Due to the fast fast-mode magnetosonic wave speed in these regions, the propagation of the wave always be affected and, therefore, exhibits some real wave characteristics such as refraction and partial reflection, which are reproduced in the numerical simulations. However, a fundamental phenomenon in wave theory, total reflection, has not yet been identified or detected. In Chapter 4, a wave train emanated from the east limb of the solar disk is analyzed in detail by using the high spatio-temporal imaging data taken from AIA/SDO. The southeastward propagating wave train reflected when it encountered a south pole CH. The detailed investigated results indicate that the wave train was totally reflected from the CH boundary because the measured incident angle and critical angle satisfy the theory of total reflection, i.e., the incident angle is smaller than the critical angle. The observed total reflection phenomenon further enriches the characteristics of the wave after it interacts with the CH. So far, all possible partial reflection, refraction, and total reflection phenomena have been observed. This study provides observational evidence for the true wave theory of coronal waves.The single, diffuse bright disturbance is always thought to be a fast-mode piston shock and bow shock driven by a CME’s expansion. Although this scenario can explain many observational features of the large-scale coronal waves, it is hard to distinguish whether a particular EUV wave is driven by a CME or ignited by a flare because the CME acceleration phase generally synchronizes with the flare’s impulsive phase. The high spatio-temporal observations from AIA/SDO indicate that some EUV waves compose multiple large-scale wavefronts. These so-called broad QFP wave trains are hard to be explained by using the CME lateral expansion theory. In Chapter 5, we study a broad QFP wave train, which occurred at the east limb of the solar disk on 2011 February 24, and find that its physical parameters, such as speed, amplitude, and energy flux, are consistent with the classical large-scale EUV wave. At the same time, the analysis result shows that the CME acceleration phase’s beginning time was behind the first wavefront’s appearance. In contrast, the beginning time of the wave train was slightly behind the onset of the flare QPPs. Combined with the above observational fact and the flare and the wave train share a common period, we believe the wave train should be triggered by the accompanying flare rather than the CME. This work provides strong evidence that the flare can drive the EUV wave.In the wave propagation process, the wave will be focused or defocused if it encounters a sudden change in the parameters of the median, such as density, temperature and magnetic field. This process is the familiar process effect of lens on waves. The lensing effect is widely used in optical systems, such as cameras, optical microscopes, and telescopes. Chapter 6 reported that a broad EUV wave train exhibited a significant focus process after transmitting through a lunate CH. Compared to the quiet-sun region, the CHs have stronger magnetic fields, lower temperatures, and smaller densities. Therefore, the CH could act as a lens system on the EUV wave propagation path. If the CH has a special shape, the wave will converge after transmitting through it. The observed lensing effect phenomenon is well reproduced in the numerical simulations. The lensing effect phenomenon of coronal waves is a strong proof of the true wave properties of coronal waves. |
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