Moffatt drift driven large scale dynamo due to alpha fluctuations with nonzero correlation times (NOTE: UNUSUAL VENUE)

by Dr Nishant Singh (Nordita)

Wednesday 29 Apr 2015, 13:30 → 14:15 Europe/Stockholm

132:028 Nordita East

We present a theory of large--scale dynamo action in a turbulent flow that has stochastic, zero--mean fluctuations of the $\alpha$ parameter. Statistically inhomogeneous $\alpha$ fluctuations give rise to finite Moffatt drift which always contributes positively to the dynamo growth if correlation time of alpha fluctuations be nonzero. We find that there exists a wavenumber cutoff at some large $k$ beyond which the growth rate turns negative. This makes it a special dynamo as the magnetic power at smallest length scales would be suppressed due to the existence of wavenumber cutoff, thus enabling a bonafide large--scale dynamo.