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DIRECT IMAGING OF QUASI-PERIODIC FAST PROPAGATING WAVES OF ∼2000 km s−1 IN THE LOW SOLAR CORONA BY THE SOLAR DYNAMICS OBSERVATORY ATMOSPHERIC IMAGING ASSEMBLY

Quasi-periodic propagating fast mode magnetosonic waves in the solar 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 Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory. In the 2010 August 1 C3.2 flare/coronal mass ejection 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−1. Similar waves propagating in opposite directions are observed in closed loops between two flare ribbons. In the k–ω 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–ω ridge shows a broad frequency distribution with power peaks 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) × 107 erg  cm−2 s−1 estimated at the coronal base is comparable to the steady-state heating requirement of active region loops.