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We present the first SDO AIA observations of a global coronal EUV disturbance(so-called "EIT wave") revealed in unprecedented detail. The disturbanceobserved on 2010 April 8 exhibits two components: one diffuse pulsesuperimposed on which are multiple sharp fronts that have slow and fastcomponents. The disturbance originates in front of erupting coronal loops andsome sharp fronts undergo accelerations, both effects implying that thedisturbance is driven by a CME. The diffuse pulse, propagating at a uniformvelocity of 204-238 km/s with very little angular dependence within its extentin the south, maintains its coherence and stable profile for ~30 minutes. Itsarrival at increasing distances coincides with the onsets of loop expansionsand the slow sharp front. The fast sharp front overtakes the slow front,producing multiple "ripples" and steepening the local pulse, and both frontspropagate independently afterwards. This behavior resembles the nature of realwaves. Unexpectedly, the amplitude and FWHM of the diffuse pulse decreaselinearly with distance. A hybrid model, combining both wave and non-wavecomponents, can explain many, but not all, of the observations. Discoveries ofthe two-component fronts and multiple ripples were made possible for the firsttime thanks to AIA's high cadences (10-20 s) and high signal-to-noise ratio.

First SDO AIA Observations of a Global Coronal EUV "Wave": Multiple Components and "Ripples"