| 其他摘要 | 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 |
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