Abstract
We are exploring the properties of precession forcing in a cylinder (ATER experiment), which shows a transition from laminar to turbulent regime when the precession rate becomes larger than a critical rate. In the laminar regime, we observe (by PIV measurement) the occurrence of a few isolated cyclonic vortices, which are lacking in the linearized solution (Kelvin waves) and have not been obtained in numerical simulations at much lower Reynolds numbers. These cyclones come from a boundary layer instability connected with the Ekman layer perturbations due to precession. They may play a crucial role in breaking the parity invariance (central symmetry) of the laminar flow. They probably could have some importance concerning the transition to turbulence.