Kinetic effects in stochastic topologically nontrivial field

The kinetic description of a collisionless system of particles in an external stochastic field possessing helicity is examined. The kinetic equation which contains an additional term proportional to the helicity is obtained. The solution describing evolution of the distribution function for arbitrary initial conditions is found. Particular examples of such an evolution and some new kinetic effects connected with helicity are discussed. It is shown that a particle beam with inhomogeneous velocity profile in an external stochastic helical field generates a new particle flow in transverse direction.