We report the first unambiguous quasi-periodic large-scale extreme-ultraviolet ( EUV ) wave or shock that was detected by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory .
During the whip-like unwinding eruption of a small filament on 2012 April 24 , multiple consecutive large-scale wavefronts emanating from AR11467 were observed simultaneously along the solar surface and a closed transequatorial loop system .
In the meantime , an upward propagating dome-shaped wavefront was also observed , whose initial speed and deceleration are about 1392 km s ^ { -1 } and 1.78 km s ^ { -2 } , respectively .
Along the solar surface , the quasi-peridoic wavefronts had a period of about 163 \pm 21 seconds and propagated at a nearly constant speed of 747 \pm 26 km s ^ { -1 } ; they interacted with active region AR11469 and launched a sympathetic upward propagating secondary EUV wave .
The wavefronts along the loop system propagated at a speed of 897 km s ^ { -1 } , and they were reflected back at the southern end of the loop system at a similar speed .
In addition to the propagating waves , a standing kink wave was also present in the loop system simultaneously .
Periodicity analysis reveals that the period of the wavefronts was consistent with that of the unwinding helical structures of the erupting filament .
Based on these observational facts , we propose that the observed quasi-periodic EUV wavefronts were most likely excited by the periodic unwinding motion of the filament helical structures .
In addition , two different seismological methods are applied to derive the magnetic field strength of the loop system , and for the first time the reliability of these inversion techniques are tested with the same magnetic structure .