STRUCTURE FORMATION AND TRANSPORT IN DISSIPATIVE DRIFT-WAVE TURBULENCE

Numerical flow simulations are used to study the effect of coherent structures on transport in the context of a two-field, two-dimensional model of dissipative drift-wave turbulence. The presence and nature of structures are found to depend on the adiabaticity parameter alpha = k(parallel-to)2 V(T)2/2-nu(ei)omega(s) which controls the degree to which the electrons respond to parallel electric fields. Transport estimates based on quasilinear and mixing-length models are compared with the simulations. In the regime with long-lived coherent structures, the turbulent particle transport predicted by a standard quasilinear or mean-field estimate is found to exceed that actually observed in the presence of coherent structures.