  Based on the system heat bath approach where the bath is nonlinearly
modulated by an external Gaussian random force, we propose a new microscopic
model to study directed motion in the overdamped limit for a nonequilibrium
open system. Making use of the coupling between the heat bath and the external
modulation as a small perturbation we construct a Langevin equation with
multiplicative noise and space dependent dissipation and the corresponding
Fokker-Planck-Smoluchowski equation in the overdamped limit. We examine the
thermodynamic consistency condition and explore the possibility of observing a
phase induced current as a consequence of state dependent diffusion and,
necessarily, nonlinear driving of the heat bath by the external noise.
