Scaling and intermittency in incoherent alpha-shear dynamo
by
Dhrubaditya Mitra
→
Europe/Stockholm
122:026
122:026
Description
We consider mean-field dynamo models with fluctuating alpha effect,
both with and without shear.
The alpha effect is chosen to be Gaussian white noise with zero mean and
given covariance.
We show analytically that the mean magnetic field does not grow, but,
in an infinitely large domain, the
mean-squared magnetic field shows exponential growth
of the fastest growing mode at a rate proportional to the shear rate.
In the absence of shear, an incoherent alpha^2 dynamo may
also be possible.
We further show by explicit calculation of the growth rate of
third and fourth order moments of the magnetic field that the
probability density function of
the mean magnetic field generated by this dynamo is non-Gaussian.
