Numerical experiments of various types of disturbances in the low and middle corona caused by solar eruptions
Based on the catastrophe model of the solar eruption, we explore the disturbances caused by solar eruptions via numerical experiments, with special attention given to large-scale waves. In addition to the phenomena shown by previous works, a new structure known as the plasma pile-up is also seen. As the disrupting magnetic structure moves outwards, a fast-mode shock is driven ahead of it. The fast-mode shock expands sideways when propagating forward and evolves to a crescent shape. Eventually the two ends of the crescent touch the bottom boundary and cause various types of disturbance behind the shock, including a shock echo. A plasma pile-up region produced by plasma accumulation behind the echo is associated with this. This is a brand new phenomenon that was not reported previously. Two features of the pile-up region draw our attention: first, its height from the bottom boundary is similar to that of some extreme ultraviolet (EUV) waves and second, its velocity is about one-third of the velocity of the fast-mode shock along the low layer of the atmosphere, which is believed to be the location of the Moreton wavefront. This suggests that the pile-up may be a source of EUV waves as well. According to our numerical results, we also synthesize the `observed' Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) images in different wavebands. The results demonstrate that the characteristics of the EUV waves `observed' in different bands are indeed different, which is consistent with the true observational results regarding EUV waves in a certain sense.