The black horizontal line and the yellow shaded region mark the volume averaged magnetic field and its uncertainties as derived from the constant B-field model (see Eq. (5)). The magnetic field configuration as derived from the MHD solution of the downstream flow (KC84) is shown for σ = 0.0045 for a shock distance between 0.13   pc < r_s < 0.15 pc, where r_s = 0.13 pc results in the upper and r_s = 0.15 pc in the lower boundary, respectively. The dashed-dotted lines mark the relative emissivity (normalized to z = 1) at specific energies. The horizontal line at 100   μG indicates a lower limit on the B-field, see Sect. 3.