Magnetic activity on the entire solar surface on 18 November 2020 during Carrington Rotation CR 2237. Panel a: SO/PHI-FDT magnetogram covers a large fraction of the far side, while a 3-day averaged SDO/HMI magnetogram shows magnetic activity on the near side. Four active regions identified on the far side by SO/PHI are outlined by red contours (see Table 1). Panel b: green-blue shades show the helioseismic phase Φ on the far side, deduced from acoustic oscillations observed on the near-side by SDO/HMI over 79 h between 17–19 November. The seismic phase is shown over a range corresponding to 1.5 − 6 times the standard deviation of the noise in the quiet Sun (σ_Φ = 2.6°).