Multivariate Linear Response Estimates of Solar Wind–Magnetosphere Coupling

Solar wind forcing and magnetospheric evolution contribute to the timing of geomagnetic disturbances. A central question is how estimated response lags depend on the chosen observable and preprocessing. We analyzed eight selected intervals of one-minute OMNI observations using multivariate covariance-based response estimates for the symmetric disturbance index in the horizontal component (SYM-H). The state contains electric field, dynamic pressure, and index levels at the current time and four preceding samples. Causal exponential high-pass filtering defines the primary analysis. Within a 0–40 min search window, the electric-field response of SYM-H increments has a median eventwise peak lag of 20 min and an interquartile range (IQR) of 10.5 min; its ensemble-mean curve peaks at 35 min. The pressure response peaks at 4 min in both summaries. Individual increment-response peak lags are unchanged across four preprocessing schemes at common timestamps. Extending the search to 120 min shifts the electric-field median to 41 min, while ensemble peaks remain at 35 and 4 min. These descriptive estimates are consistent with rapid compressive and slower convective contributions, but window dependence, model approximation, and interpolated inputs limit their interpretation as physical transport delays.