Dynamics of light particles in oscillating cellular flows

The dynamics of light particles in chaotic oscillating cellular flows is investigated both analytically and numerically by means of Monte Carlo simulations. At level of linear analysis (in the oscillation amplitude) we determined how the known fixed points relative to the stationary cellular flow deform into closed stable trajectories. Once the latter have been analytically determined, we numerically show that they possess the dynamical role of attracting all asymptotic trajectories for a wide range of parameters values. The robustness of the attracting trajectories is tested by adding a white-noise contribution to the particle equation of motion. As a result, attracting trajectories persist up to a critical Péclet number above which an average rising velocity sets in. Possible implications of our results on the long-standing problem related to the explanation of the observed oceanic plankton patchiness will be also discussed.