Panel a: radial magnetic field component B_r that is taken from the NLFFF evolutionary model and used as the lower boundary in the initial condition of the MHD simulation. The map of the surface magnetic field is shown using Mollweide projection where black (white) represents positive (negative) magnetic field regions. The region of the solar disk visible from SDO/Earth is represented by the red circles, AR 12253 and the large AR complex behind the east limb are labelled in white. Panel b: radial component of the Lorentz force LF_r at the solar surface.