This page contains movies of hydrodynamical simulations of Corotating Interaction Regions (CIRs).
In a radiatively driven stellar wind, a bright spot on the surface creates a perturbance (a CIR) which travels through the wind.
This CIR is seen as a spiral-shaped density enhancement, compared to the smooth wind. The CIR also perturbs the velocity field.
CIRs are responsible for the Discrete Absorption Components seen in some ultraviolet resonance lines of hot stars.

This work has been published in Lobel & Blomme (2008, ApJ, 678, 408). Click here for the ADS link. Conference proceedings of this work can be found here and here .

This webpage concentrates on the hydrodynamics of the CIRs. Their relation to Discrete Absorption Components is discussed here.

Simulations

All these simulations were made using the Zeus3D hydrodynamics code (Stone and Norman 1992).
The star and wind parameters are those of the B0.5 Ia star HD 64760.

Movies

Each movie comes in AVI and MP4 format.

The colour scale is used to show the density contrast with respect to a smooth wind.
The velocity vectors are those with respect to a smooth wind. The length scale of the velocity vectors can differ from one movie to the other.
Each movie shows two rotations of the CIR. All movies run at the same "speed", but the real time taken for a spot pattern to rotate will depend on the model.

AVI	MP4	one spot on the stellar surface A=0.10; Phi=50 degrees; vspot=vrot/2.5; 1 rotation of spot=10.3 days minimum density contrast=0.99 maximum density contrast=1.21 largest velocity vector=91 km/s
AVI	MP4	one spot on the stellar surface A=0.10; Phi=50 degrees; vspot=vrot/2.5; 1 rotation of spot=10.3 days Trace particles have been added to show their nearly-radial outflow (except very close to the stellar surface where they rotate due to angular momentum conservation). The particles emitted at the centre of the CIR do not remain in the CIR, but go through it. The CIR is not a stream of particles, but a pattern in the wind. A circle (centred on the star) is drawn through the green point that started at the centre of the CIR. This helps to see the (small) velocity differences between the different trace particles.
AVI	MP4	two spots on the stellar surface, each one A=0.20; Phi=20 degrees; vspot=vrot/5; 1 rotation of spots=20.6 days minimum density contrast=0.87 maximum density contrast=1.32 largest velocity vector=143 km/s
AVI	MP4	two different spots on the stellar surface, with A=0.20; Phi=20 degrees, and A=0.08; Phi=30 degrees; vspot=vrot/5; 1 rotation of spots=20.6 days minimum density contrast=0.88 maximum density contrast=1.32 largest velocity vector=143 km/s
AVI	MP4	one spot on the stellar surface A=0.50; Phi=180 degrees; vspot=vrot/10; 1 rotation of spot=41.2 days minimum density contrast=1.00 maximum density contrast=1.97 largest velocity vector=226 km/s
AVI	MP4	one spot on the stellar surface A=0.50; Phi=90 degrees; vspot=vrot*3; 1 rotation of spot=1.373 days minimum density contrast=0.95 maximum density contrast=2.07 largest velocity vector=180 km/s
AVI	MP4	one dark spot on the stellar surface A=-0.30; Phi=30 degrees; vspot=vrot/2.5; 1 rotation of spot=10.3 days minimum density contrast=0.55 maximum density contrast=1.53 largest velocity vector=380 km/s
AVI	MP4	four spots on the stellar surface, each one A=0.10; Phi=30 degrees; vspot=vrot/10; 1 rotation of spots=41.2 days minimum density contrast=0.96 maximum density contrast=1.16 largest velocity vector=88 km/s