Temporal evolution of the physical properties of P1. Panel A: magnetic field intensity derived from the inversions (black line); LOS magnetic flux density from COG (red line) and from the inversions (black thin line); the shadow represents a range of  ± 50 G around the magnetic flux density values from the inversions. Panel B: photospheric LOS velocity derived from the inversions (black line) and from the Stokes V zero-crossing (red line). Panel C: LOS magnetic field inclination derived from the inversions (black line) and from the strong field approximation (red line). Panel D: magnetic filling factor derived from the inversions. Panel E: chromospheric LOS velocity derived from the core shift of Ca ii line. The arrows mark the times corresponding to the frames shown in Fig. 2 from second column on. Minor horizontal tick marks are spaced 52 s.