Boundary condition at the lower side of the box. (a) The artificial magnetogram (Gauss), (b) distribution of plasma pressure (dyn/cm²), and (c) distribution of plasma density (gr/cm³). In panel (a), the arrows represent the horizontal components of the magnetic field in the photosphere$\left(B_x\widehat{i}+B_y\widehat{j}\right)$. The intensity of the radial component of the magnetic field, | B_ɀ |, is displayed via the colormap.