Helioseismic phase shift Φ versus unsigned line-of-sight magnetic field |B_los|, both averaged over each of the six active regions on the far side (blue dots). Active region areas are determined from SO/PHI magnetograms (red contours in Figs. 2 and A.1). The numerical values are provided in Table 1 and the error bars refer to ±1σ_Φ seismic noise. The blue solid line is a linear fit with slope −0.2 deg G⁻¹ and intercept (5 G, 0°).