We compare transport statistics of elongated incompressible shearing boxes for different Reynolds and magnetic Prandtl numbers , Re and Pm , and aspect ratios , L _ { z } / L _ { x } .
We find that at fixed aspect ratio L _ { z } / L _ { x } = 4 and Re = 10 , 000 , the turbulent stresses for Pm \lesssim 1 do not show considerable variation and follow a power law \sim Pm ^ { 3 / 2 } for Pm > 1 .
This is qualitatively consistent with previous results based on net imposed flux and small box L _ { z } / L _ { x } \sim 1 simulations but the power law exponent is different .
The saturated level of stresses , the ratio of Maxwell stress to the magnetic energy and Reynolds to Maxwell stress ratio are roughly invariant as L _ { z } / L _ { x } is increased .
For cases where the boxes are elongated in both the azimuth and vertical direction , the transport coefficient \alpha \in [ 0.1 , 1.0 ] that is 10 - 100 times larger than the case with L _ { y } / L _ { x } = 2 and large L _ { z } / L _ { x } .
Overall , our results suggest that the saturated state of turbulence is sensitive to both dissipation coefficients and aspect ratio ( both L _ { z } / L _ { x } , L _ { y } / L _ { x } ) motivating further work on this problem .