Coronal magnetic field from the two-dipole model. Average coronal magnetic field during the three solar minima obtained from the two-dipole model of the photospheric field using the PFSS model. The coronal source surface, where magnetic field lines (in blue) become purely radial is marked with a dashed circle. The photospheric radial magnetic field observed during Carrington rotation 1910 in year 1996 is shown on the solar surface, featuring typical unipolar regions at the poles, with yellow and blue colors indicating positive (away from the Sun) and negative (toward the Sun) magnetic polarity, respectively. The heliospheric current sheet is shifted towards the south by 4.1°.