  The paper defines and discusses the concept of hidden drifts in
two-dimensional turbulence. These are ordered components of the trajectories
that average to zero and do not produce direct transport. Their effects appear
in the evolution of the turbulence as a special type of fluxes, which consist
of average motion of positive and negative fluctuations in opposite directions.
We show that these fluxes have important nonlinear effects in turbulent fluids
and in confined plasmas. In the first case, they determine the increase of the
large scale vorticity and velocity at the expense of the small scale
fluctuations by a process of separation of the vorticity fluctuations according
to their sign. In the second case, they provide a mechanism for zonal flow
generation and a vorticity flux that influences the sheared rotation of the
plasma.
