Hyperbolic diffusion with Christov–Morro theory

We employ recent ideas of C.I. Christov and of A. Morro to develop a theory for diffusion of a solute in a Darcy porous medium taking convection effects into account. The key point is that the solute evolution is not governed by a parabolic system of equations. Indeed, the theory developed is basically hyperbolic. This still leads to a model which allows for convective (gravitational) overturning in a porous layer, but in addition to the classical mode of stationary convection instability there is the possibility of oscillating convection being dominant for a lower salt Rayleigh number, if the relaxation time is sufficiently large.