Time series of the intercept − v/u (a and b) and the slope parameter u (c and d) calculated for the north and south poles from data of EUVI A (in red), EUVI B (in blue), and EIT (in green) in the wavelength of 171 Å. The contributions of the different instruments are indicated by different colors. As explained in the text, the intercept is proportional to the projected heliographic colatitude of the magnetic pole location. The slope is a measure of the projected opening factor f_c of the polar magnetic field at the respective pole (see labeling of the respective right ordinate axes).