Magnetic field polarity configuration at different heights. Results shown for a prolate ellipsoidal source surface with ellipticity 2.0 (left column), for the classical spherical source surface (center), and for an oblate ellipsoidal surface again with ellipticity 2.0 (right). All figures were created using our grid solver. The source surface height for all models is 2.5 R_⊙ (minor half-axis in the ellipsoidal cases). Depicted is Carrington rotation 2066. Data for the lower boundary was obtained from MDI onboard SOHO. First row: three-dimensional rendering of a few magnetic field lines for each model as well as a cut through the height levels depicted below. Rows 2 to 5: magnetic field polarity configuration at height levels 1.0R_⊙, 1.5R_⊙, 2.0R_⊙, and 2.5R_⊙ (minor half-axis/radius) in a synoptic Carrington format. The height levels correspond to ellipsoids at distances of 0%, 33%, 67%, and 100% between the photosphere and source surface. Red magnetic field lines and pixels are directed inward, blue lines are directed outward, and cyan indicates closed field structures. The projection of Earth on the height levels is drawn as a black ascending line near the solar equator. Black ellipses, circles, and squares are inserted to highlight differences in the regimes of interest (see text for details).