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We present two-dimensional hydrodynamical simulations of corotating streamstructure in the wind from a rotating O star, together with resulting syntheticline profiles showing discrete absorption components (DACs). An azimuthalvariation is induced by a local increase or decrease in the radiative drivingforce, as would arise from a bright or dark ``star spot'' in the equatorialplane. Since much of the emergent wind structure seems independent of the exactmethod of perturbation, we expect similar morphology in winds perturbed bylocalized magnetic fields or nonradial pulsations, as well as by eitherrotationally-modulated structure or transient mass ejections. We find thatbright spots with enhanced driving generate high-density, low-speed streams,while dark spots generate low-density, high-speed streams. Corotatinginteraction regions (CIRs) form where fast material collides with slow material-- e.g. at the leading (trailing) edge of a stream from a dark (bright) spot,often steepening into shocks. The unperturbed supersonic wind obliquely impactsthe high-density CIR and sends back a nonlinear signal which takes the form ofa sharp propagating discontinuity (``kink'' or ``plateau'') in the radialvelocity gradient. These features travel inward in the co-moving frame at theradiative-acoustic characteristic speed, and thus slowly outward in the star'sframe. We find that these slow kinks, rather than the CIRs themselves, are morelikely to result in high-opacity DACs in the absorption troughs of unsaturatedP Cygni line profiles.

Hydrodynamical Simulations of Corotating Interaction Regions and Discrete Absorption Components in Rotating O-Star Winds