We present an observational study of a quasi-periodic fast propagating (QFP) magnetosonic wave on 2012, April 23. The multiple wave trains were observed along an active region open loop system which has a divergence geometry. The wave trains were first observed in 171 A observations at a distance of 150 Mm from the footpoint of the guiding loop system and with a speed of 689 km/s, then they appeared in 193 A observations after their interaction with a perpendicular underlaying loop system on the path, in the meantime, the wave speed decelerated to 343 km/s quickly within a short timescale. The sudden deceleration of the wave trains and their appearance in 193 A observations caused by the interaction are interpreted through geometric effect and the density increase of the guiding loop system, respectively. On the other hand, with Wavelet and Fourier analysis methods we find that the wave trains has a common period of 80 s with the associated flare. In addition, a few low frequencies are also identified in the QFP wave. We propose that the generation of the period of 80 s was caused by the periodic releasing of energy busts through some nonlinear processes in magnetic reconnection or the so-called oscillatory reconnection mechanism, while the low frequencies detected in the QFP wave were possibly the manifestations of the leakage of pressure-driven oscillations from the photosphere or chromosphere, which could be an important source for driving QFP waves in the low corona. Our observational 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. Therefore, QFP waves could be used for remote diagnostics of the local physical properties of the solar corona.
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