Simulated high-energy coronal emission vs. unsigned radial magnetic flux ⟨Φ_Br⟩_s. Each point corresponds to one of the simulations described in Sect. 4, including the solar cases as indicated. These values are calculated from synthetic spectra, based on the EM(T) distributions (Sect. 5.1), and integrated in the SXR (2−30 Å, green), X-ray (5−100 Å, red) and EUV (100−920 Å, blue) bands. The solid lines correspond to fits to the simulated data points. The dashed lines are based on observational studies using X-ray, against magnetic field measurements using ZB (Pevtsov et al. 2003) and ZDI (Vidotto et al. 2014).