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Using direct numerical simulations (DNS) we verify that in the kinematicregime, a turbulent helical dynamo grows in such a way that the magnetic energyspectrum remains to high precision shape-invariant, i.e., at each wavenumber$k$ the spectrum grows with the same growth rate. Signatures of large-scaledynamo action can be identified through the excess of magnetic energy at small$k$, of one of the two oppositely polarized constituents. Also a suitablydefined planar average of the magnetic field can be chosen such that its rmsvalue isolates the strength of the mean field. However, these different meansof analysis suggest that the strength of the large-scale field diminishes withincreasing magnetic Reynolds number ${\rm Re}_{\rm M}$ like ${\rm Re}_{\rmM}^{-1/2}$ for intermediate values and like ${\rm Re}_{\rm M}^{-3/4}$ forlarger ones. Both an analysis from the Kazantsev model including helicity andthe DNS show that this arises due to the magnetic energy spectrum still peakingat resistive scales, even when helicity is present. As expected, the amplitudeof the large-scale field increases with increasing fractional helicity,enabling us to determine the onset of large scale dynamo action anddistinguishing it from that of the small-scale dynamo. Our DNS show that,contrary to earlier results for smaller scale separation (only 1.5 instead ofnow 4), the small-scale dynamo can still be excited at magnetic Prandtl numbersof 0.1 and only moderate values of the magnetic Reynolds numbers ($\sim 160$).

Traces of large-scale dynamo action in the kinematic stage