This book is profound to an account of theoretical study of convective instability in a ferrofluid saturated porous layer which involve local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) effects. It is written for post graduate students and researchers in applied mathematics. The term "local thermal equilibrium" denotes to thermomagnetic convection in a ferrofluid saturated porous layer where the solid-phase temperature is equal to the fluid temperature at any location in the porous media, so that the heat transfer processes in the two phases can be lumped into a process described by a single energy equation. To be specific, the LTE is considered at the macroscopic scale and not at the pore scale. The term "local thermal non-equilibrium" refers that the single energy equation is replaced with two energy equations, one for the solid phase and the other for the fluid phase. This is an attempt to observe the effects of magnetic field dependent viscosity, uniform internal heat generation, and vertical heterogeneity of permeability on thermal convection in a ferrofluid-saturated porous medium using traditional LTE and LTNE models.