Suppression of Transport Cross Phase by Strongly Sheared Flow

A generic model for advection of a scalar by $\mathbf{E}\times \mathbf{B}$ flow with a linearly varying mean shows that the cross phase factor in the transport flux is strongly reduced in the strong shear regime (shearing $\mathrm{rate}>\mathrm{eddy}$ turnover rate), leading to significant transport suppression. The cross phase scales much more strongly with shear strength than do fluctuation amplitudes, allowing significant transport reduction even if fluctuations increase, or decrease only slightly. Cross-phase suppression thus can be the dominant transport-reduction mechanism in transport barriers.