Using the earth-orbiting spacecraft IMP-8, we have performed a high time-resolution (2.5-min) study of the linear cross-correlations of a quantitative indicator of magnetospheric substorm activity, the auroral electrojet (AE) index, with several interplanetary (IP) parameters. The present study includes all available satellite data (from an eight-month period) rather than selecting a small number of substorm events, or a relatively small number of chosen days. Prior published studies have suggested that geomagnetic activity is related to a variety of solar wind parameters: solar wind speed (V); north-south magnetic field component (Bz); total interplanetary magnetic field (IMF) strength (B); and various combinations of these parameters. Very recently, a new parameter, &egr;( = VB2 sin4(ϑ/2)l0 2), has been suggested as a superior predictor of substorm activity. The other major preferred correlator with geomagnetic activity is VB8, where B8 is the southward (Bz<0) component of the IMF. Substantial discussion has ensued as to which parameters is the ''best'' predictor of substorm activity. The present non-selective, high-resolution analysis reveals that VB8 generally reaches a higher peak correlation than &egr; (0.6 vs 0.54). Both parameters reach a peak correlation at the same lag time (with AE lagging the IP parameters by ~40 min.), but VB8 also appears to have a preferable qualitative lag profile shape for AE prediction purposes.