  Quasi-periodic, propagating fast mode magnetosonic waves in the corona were
difficult to observe in the past due to relatively low instrument cadences. We
report here evidence of such waves directly imaged in EUV by the new SDO AIA
instrument. In the 2010 August 1 C3.2 flare/CME event, we find arc-shaped wave
trains of 1-5% intensity variations (lifetime ~200 s) that emanate near the
flare kernel and propagate outward up to ~400 Mm along a funnel of coronal
loops. Sinusoidal fits to a typical wave train indicate a phase velocity of
2200 +/- 130 km/s. Similar waves propagating in opposite directions are
observed in closed loops between two flare ribbons. In the k-$\omega$ diagram
of the Fourier wave power, we find a bright ridge that represents the
dispersion relation and can be well fitted with a straight line passing through
the origin. This k-$\omega$ ridge shows a broad frequency distribution with
indicative power at 5.5, 14.5, and 25.1 mHz. The strongest signal at 5.5 mHz
(period 181 s) temporally coincides with quasi-periodic pulsations of the
flare, suggesting a common origin. The instantaneous wave energy flux of
$(0.1-2.6) \times 10^7 ergs/cm^2/s$ estimated at the coronal base is comparable
to the steady-state heating requirement of active region loops.
