  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.
