选址与日冕观测组知识库

We present observations of a quasi-periodic fast-propagating (QFP) magnetosonic wave on 23 April 2012, with high-resolution observations taken by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Three minutes after the start of a C2.0 flare, wave trains were first observed along an open divergent loop system in 171 observations at a distance of 150 Mm from the footpoint of the guiding loop system and with a speed of 689 km s(-1), then they appeared in 193 observations after their interaction with a perpendicular, underlaying loop system on the path; in the meantime; their speed decelerated to 343 km s(-1) within a short time. The sudden deceleration of the wave trains and their appearance in 193 observations are interpreted through a geometric effect and the density increase of the guiding loop system, respectively. We find that the wave trains have a common period of 80 seconds with the flare. In addition, a few low frequencies are also identified in the QFP wave. We propose that the generation of the period of 80 seconds was caused by the periodic releasing of energy bursts through some nonlinear processes in magnetic reconnection, while the low frequencies were possibly the leakage of pressure-driven oscillations from the photosphere or chromosphere, which could be an important source for driving coronal QFP waves. Our results also indicate that the properties of the guiding magnetic structure, such as the distributions of magnetic field and density as well as geometry, are crucial for modulating the propagation behaviors of QFP waves.