Revision of empirical electric field modeling in the inner magnetosphere using Cluster data

Abstract

Using Cluster data from the Electron Drift (EDI) and the Electric Field and Wave (EFW) instruments, we revise our empirically‐based, inner‐magnetospheric electric field (UNH‐IMEF) model at 2<L<10. We pick more EFW data during large activities when wake effects are expected to be small. The model is organized by either the interplanetary electric field (IEF) merging with the magnetosphere or the Kp index. IEF and Kp ranges for which we get potential patterns are, respectively: IEF<0.282 mV/m, 0.282<IEF<0.575 mV/m, 0.575<IEF<0.872 mV/m, 0.898<IEF<1.308 mV/m, 1.308<IEF<1.834 mV/m, 1.834<IEF<2.662 mV/m, and IEF>2.662 mV/m; Kp<1, 1≤Kp<2, 2≤Kp<3, 3≤Kp<4, 4≤Kp<5, and Kp≥4+. Patterns consist of one set of data and processing for smaller activities, and another for higher activities. As activity increases, the skewed potential contour related to the partial ring current appears on the nightside. With the revised analysis, we find that the skewed potential contours get clearer and potential contours get denser on the nightside and morningside. Since the fluctuating components are not negligible, standard deviations from the modeled values are included in the model. In this study, we perform validation of the derived model more extensively. We find experimentally that the skewed contours are located close to the last closed equipotential, consistent with previous theories. This gives physical context to our model and serves as one validation effort. As another validation effort, the derived results are compared with other models/measurements. From these comparisons, we conclude that our model has some clear advantages over the others.