An Evaluation of Equatorial Perturbation Electric Fields Using Empirical Vertical Drift Models

Abstract We examined the electrodynamic impact of four geomagnetic storms of increasing intensities on the equatorial ionosphere: a moderate storm (27–28 September 2017), a strong storm (17–18 April 2002), a severe storm (07–08 September 2017), and an extreme storm (09–10 November 2004). Using Jicamarca incoherent scatter radar data, we analyzed F‐region height‐averaged vertical drift residuals to study perturbations in the zonal equatorial electric field, including effects from the interplanetary magnetic field (IMF) B z component, substorms, and ionospheric disturbance dynamo (DD). We compared the zonal electric field effects from these storms with predictions from three empirical equatorial vertical drift models: Fejer and Scherliess (1997, https://doi.org/10.1029/97ja02164 ) (F‐S), Kelley and Retterer (2008, https://doi.org/10.1029/2007sw000381 ) (K‐R), and Manoj and Maus (2012, https://doi.org/10.1029/2012sw000825 ) (M‐M). Our findings show that these models often fail to predict equatorial disturbance electric fields accurately. The K‐R prompt penetration model performed best for the most intense storm, reflecting a strong correlation between the interplanetary electric field (IEF) and the equatorial zonal electric field. The F‐S prompt penetration model performed reasonably well in moderate storms, indicating that auroral electrojet indices alone are insufficient for accurate predictions. The M‐M model followed equatorial drift trends only during and shortly after significant IEF changes and away from the terminator. The F‐S DD model performed best for the postmidnight period during the recovery phase of moderate storms. These results highlight the need for models that incorporate additional parameters, such as the IMF By and substorm effects, to better predict ionospheric responses to geomagnetic storms.