A tensor transfer-function model of the equatorial ionospheric eastward electric field driven by ACE solar wind data

A significant portion of the short-period variability of the equatorial ionospheric electric field (EEF) can be explained by prompt penetration (PP) of the inter-planetary electric field (IEF). By combining a climatological model with a PP model driven by solar wind measurements, one can thus predict the EEF in real time. Manoj et al. (2008) proposed a transfer-function-based model to predict EEF variations due to prompt penetration of the IEF. This model is driven by the solar-wind electric field data from the ACE satellite and is limited to the day-time. The model could account for around 30% of the variability found in the JULIA radar measurements EEF. We propose two improvements to our model: 1) We estimate a transfer-function tensor between the interplanetary electric field vector and the equatorial electric field. Previously we considered only the dawn-dusk (Ey) component of the IEF vector. 2) We introduce local-time and seasonal dependencies to our model by correlating the EEF data derived from the Jicamarca ISR with the IEF data. In general, PP is maximally efficient for the variations in the IEF with 2- hour periodicity. The magnitude of penetration of IEF Ez to EEF is an order of magnitude smaller than that of IEF Ey. The diurnal curve of the correlation between IEF and EEF shows the well-known reversals of polarity at dawn and dusk. In addition, the correlation reduces at local noon, owing to the increased conductivity of the ionosphere. The paper discusses the implications of these results in predicting the EEF.