  Nonhelical shear dynamos are studied with a particular focus on the
possibility of coherent dynamo action. The primary results -- serving as a
follow up to the results of Squire & Bhattacharjee [arXiv:1506.04109 (2015)] --
pertain to the "magnetic shear-current effect" as a viable mechanism to drive
large-scale magnetic field generation. This effect raises the interesting
possibility that the saturated state of the small-scale dynamo could drive
large-scale dynamo action, and is likely to be important in the unstratified
regions of accretion disk turbulence. In this paper, the effect is studied at
low Reynolds numbers, removing the complications of small-scale dynamo
excitation and aiding analysis by enabling the use of quasi-linear statistical
simulation methods. In addition to the magnetically driven dynamo, new results
on the kinematic nonhelical shear dynamo are presented. These illustrate the
relationship between coherent and incoherent driving in such dynamos,
demonstrating the importance of rotation in determining the relative dominance
of each mechanism.
