Effects of unsteady sheared $\bf E \times B$ flow on slab ITG turbulence

Effects of unsteady sheared $\bf E \times B$ flow on drift wave turbulence and heat transport driven by slab ion temperature gradient (ITG) instability are investigated by means of Landau fluid simulations. Here, the $\bf E \times B$ flow, which consists of stationary and time-periodic oscillatory parts, is externally applied to the turbulence. The dependence on the amplitude and frequency of $\bf E \times B$ flow are examined in the case where the energy of $\bf E \times B$ flow is the same or larger than the energy of turbulence. In the case above, the transport oscillates with the same period as the $\bf E \times B$ flow and the time-averaged transport coefficient is larger than the coefficient which is evaluated without oscillatory part of $\bf E \times B$ flow. The time-averaged coefficient is maximized at the point where the amplitude of oscillatory part is equal to that of stationary part. As the frequency of $\bf E \times B$ flow increases, the time-averaged coefficient decreases and is close to the coefficient which is evaluated without oscillatory part. These mechanisms are explained.