On the Reynolds stress and zonal flows in the edge of tokamaks.

It is well known that turbulence, the major candidate to explain anomalous transport, can be quenched by sheared flows which rip the convective cells apart, thus forming a barrier. The op-posite mechanism, i.e. the turbulence generating a macroscopical sheared flow, has been studied as well, both on the theoretical side [1], as on the experimental one [2]. Knowing that the tur