We experimentally investigated the temporal dynamics and the different transitions associated to the generation of large scale coherent structures in two-dimensional turbulence (2D). For a given dissipation rate, the increase of energy injected into the system gives rise to the formation of a large scale circulation, with spatial structures and temporal dynamics, which differ from the small-scale turbulent background. We have quantified a transition over a turbulent background . Moreover, the large scale flow exhibits a spectral signature commonly called " 1/f noise". As the forcing increases, we observed the emergence of a spatial configuration of vorticity. This state is often called , by analogy to the Bose-Einstein condensate, condensed regime. Due to the symmetry of the forcing, the large-scale flow may rotate in both directions. We observed stochastic reversals of the direction of the large-scale flow. The properties of these reversals are compared with the models proposed to explain reversals of Earth's magnetic field.
