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

Dynamo effect is considered in more general case than well known one when n ot only mean motion but also conducting components possess nonzero mean hel icity. Dispersion equation for helical motions is studied, including inhomo geneous case. Criteria for development of instability are found. Interactio n between large-scale internal wave and small-scale helical turbulence in p lane Couette flow of fluid with statically stable uniform density gradient in gravitational field is studied basing on a set of equations for scalar a nd quasi-scalar wave fields and for helicity of turbulence. This system of equation describes acceleration of wave growth due to its backward action o n turbulence, i.e. wave-turbulent instability. Chiral media are further con sidered 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. (C) 1999 Elsevier Science Ltd. All rights reserved.