PDF of the strength of magnetic field B for the SSD F (blue), G (black), K (green) and M star (red). Top: PDF of B calculated for the geometric surface z_〈τ〉 = 1 corresponding to the height at which 〈τ〉 = 1. Bottom: same plot as the top, but for the iso τ = 1 surface. The vertical lines correspond to the pressure equipartition field (dotted) and (dashed) for each case (see Sect. 4.1 for details of the description of B_eqp,tot). The labels contain the mean value for each case in gauss.