Simultaneous data from the years 2001 and 2002. In each case the data have been averaged into 365 equal-sized bins of time-of year F (one day long for these non-leap years) and then a running mean taken over 27 bins to cover whole solar rotation intervals. From top to bottom: (a) the half-wave rectified dawn-to-dusk electric field, E_DD, in interplanetary space; (b) the AU index; (c) the AL index; (d) the polar cap flux, W_PC, from the DMSP satellite data; (e) the transpolar voltage, Φ_PC, from the DMSP satellite data; (f) the reconnection efficiency assuming that the cross-sectional radius of the magnetosphere is 15 R_E (where a mean Earth radius 1 R_E = 6370 km), η₁₅; (g) the am geomagnetic index; and (h) the ratio of the am index to the transpolar voltage, am/Φ_PC. In panels (d) and (e) for W_PC and Φ_PC, the red and blue lines are for the northern and southern polar caps, respectively.