EXPERIMENTAL-OBSERVATION OF THE 2-DIMENSIONAL INVERSE ENERGY CASCADE

We report the first clear experimental evidence of a stationary two-di mensional inverse energy cascade. The experiments are performed in ele ctromagnetically driven flows, using thin, stably stratified layers; m easurements of the instantaneous velocity fields show that the fluctua tions are homogeneous and isotropic in the inertial range. The energy spectrum displays the expected k(-5/3) law with a Kolmogorov constant lying in the range 5.5-7, which is consistent with the current numeric al estimates.