We study the structure of a magnetoconvective flow. The magnetic field modifies the heat fluxes at the walls. It tends to destroy the three-dimensional patterns in favor of two-dimensional rolls. The last part of this paper consists in an extent to the marginal stability theory, thanks to a finite difference scheme. We also present the validation of the developments of the finite volume code Jadim, thanks to the simulation of magnetohydrodynamic (MHD) flows that have analytical solutions
