IMF, HCCSSS, and PFSS unsigned open flux. In both plots, the heliospheric open flux calculated from the IMF OMNI 2 database is plotted by the black line. Top: HCCSSS open flux is plotted against IMF open flux for HCCSSS cusp surface heights of ﹩1.7{R}_{\odot }﹩ (upper line, blue) and ﹩1.9{R}_{\odot }﹩ (lower line, red). Bottom: PFSS open flux at source surfaces of 2.0 R_⊙ (upper line, blue) and 2.2 R_⊙ (lower line, red) are plotted against IMF open flux.