Representation of the magnetic-field structure and strength (in colours) of one of the prestellar-core models from Li & Shu (1996). These models are for isothermal cores at magnetostatic equilibrium. The example is shown for λ_r = 1.52. The black circle in the middle, with a diameter of ~0.1 pc, indicates the region used to average the magnetic-field strength. The 3D rendering was made with the ParaView software (http://www.paraview.org).