Amplification of fluctuations and current dynamo due to helical and chiral effects in geophysical and plasma-like media

Abstract

Dynamo effect is considered in more general case than well known one when not only mean motion but also conducting components possess nonzero mean helicity. Dispersion equation for helical motions is studied, including inhomogeneous case. Criteria for development of instability are found. Interaction between large-scale internal wave and small-scale helical turbulence in plane Couette flow of fluid with statically stable uniform density gradient in gravitational field is studied basing on a set of equations for scalar and quasi-scalar wave fields and for helicity of turbulence. This system of equation describes acceleration of wave growth due to its backward action on turbulence, i.e. wave-turbulent instability. Chiral media are further considered and effects topologically close to helical ones are analyzed. It is shown that in such media ranges of scales exist, in which fluctuations of electric field can be anomalously amplified.