| 其他摘要 | ``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. |
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