We present a method for estimating the portion of the ionospheric high‐latitude potential that maps to the magnetospheric boundary layer during steady northward IMF and global ionospheric 4‐cell convection patterns associated with lobe reconnection, together with the results of a statistical study based on DMSP F13 data from 1996–2004. In comparison with a previous study for steady southward IMF by K. Å. T. Sundberg et al. (2008), the results show significantly larger boundary layer potentials, with a mean value of 10 kV for the 271 events studied, corresponding to roughly 30–35% of the potential generated by the solar wind interaction. In a statistical analysis, the boundary layer potential is also shown to depend significantly on viscous parameters such as the solar wind velocity, density and pressure.