KP synoptic maps for Carrington rotation 1999. Left column: Photospheric magnetic field. The magnetogram was smoothed with a Gaussian smoothing kernel with a standard deviation of 3. The black lines correspond to B  =   ± 10 G contours. Center column: KP PFSS source surface magnetic field. The black lines correspond to B  =   ± 0.15 G contours. Right column: Coronal holes from the McIntosh archive. Yellow and blue correspond to positive and negative polarity in all maps. The dashed red and blue lines mark the vector sum longitude and its opposite. The red and cyan circles mark the vector sum direction and its antipode.