The technique of empirical linear prediction filters is used to investigate the extent to which the low latitude dawn-dusk magnetic asymmetry is controlled by the dawn-dusk solar wind motional electric field VBs and/or by substorm processes measured by the westward auroral electrojet index AL. The dawn-dusk asymmetry is measured by a new index defined as the difference between dawn and dusk deviations in the X (geomagnetic Northward) magnetic field component. The empirically determined filters obtained from this analysis provide quantitative information which characterizes the coupling processes. For example, the VBs to AL filter is a delayed pulse beginning after a delay of about 15 minutes, peaking at 60 minutes and returning to zero at 120 min. The filter has the characteristics of a low pass filter with a cutoff frequency at 10-4 Hz. The VBs to ASYM filter is also a delayed pulse with similar constants. The VBs to ASYM filter, however, also has a long tail which gradually decays reaching zero near 5 or 6 hours lag time. The AL to ASYM filter is acasual, being nonzero at future lag times. The peak of the filter occurs at a delay of about 10 min. and decays exponentially becoming nearly zero after 4 hours lag. Our results indicate that some currents are directly driven by the solar wind-magnetosphere interaction and that their magnetic perturbations contribute to both the AL and ASYM indices. A portion of the AL index that is uncorrelated with VBs is, however, correlated with ASYM suggesting that internal magnetospheric processes contribute to AL and ASYM as well.