We study effects of random fluid motion on a system in a self-organized
critical state. The latter is described by the continuous stochastic model, proposed
by Hwa and Kardar [Phys. Rev. Lett. 62: 1813 (1989)]. The advecting velocity
field is Gaussian, not correlated in time, with the pair correlation function of the form
∝ δ(t − t
′
)/kd−1+ξ
⊥ , where k⊥ = |k⊥| and k⊥ is the component of the wave vector,
perpendicular to a certain preferred direction – the d-dimensional generalization of the
ensemble introduced by Avellaneda and Majda [Commun. Math. Phys. 131: 381
(1990)]. Using the field theoretic renormalization group we show that, depending on
the relation between the exponent ξ and the spatial dimension d, the system reveals
different types of large-scale, long-time scaling behaviour, associated with the three
possible fixed points of the renormalization group equations. They correspond to
ordinary diffusion, to passively advected scalar field (the nonlinearity of the Hwa–
Kardar model is irrelevant) and