We analyze the initial , kinematic stage of magnetic field evolution in an isotropic and homogeneous turbulent conducting fluid with a rough velocity field , v ( l ) \sim l ^ { \alpha } , \alpha < 1 .
We propose that in the limit of small magnetic Prandtl number , i.e .
when ohmic resistivity is much larger than viscosity , the smaller the roughness exponent \alpha , the larger the magnetic Reynolds number that is needed to excite magnetic fluctuations .
This implies that numerical or experimental investigations of magnetohydrodynamic turbulence with small Prandtl numbers need to achieve extremely high resolution in order to describe magnetic phenomena adequately .