E‐Field Effects on Day‐To‐Day Variations of Geomagnetic Mid‐Latitude Sporadic E Layers

Abstract

AbstractThis study investigates the effects of the electric fields (E‐fields) on day‐to‐day variations in geomagnetic mid‐latitude sporadic E layers (EsLs) using a numerical ionospheric model. It is widely accepted that geomagnetic mid‐latitude EsL dynamics depend largely on wind shear variations. In contrast, E‐field effects on geomagnetic mid‐latitude EsLs have not been investigated extensively and are still little known. Previous observations have reported that E‐fields change EsL heights by only several kilometers. However, no studies have investigated E‐field effects on day‐to‐day EsL variations. Recently, our numerical ionospheric model succeeded generally in reproducing day‐to‐day EsL variations driven by winds at geomagnetic mid‐latitudes. In this study, using the ionospheric model, we conducted EsL simulations including both E‐fields and winds, to elucidate how E‐fields affect day‐to‐day EsL variations at geomagnetic mid‐latitudes. It was found that zonal and meridional/vertical E‐fields change the vertical EsL dynamics above ∼110 km. Below ∼130 km, where most Es layers appear, vertical/meridional E‐fields are more effective for EsL dynamics than zonal E‐fields. During the day, E‐fields pump metal ions from the lower ionosphere to more than 110 km. Pumping facilitates the formation of daytime EsLs above ∼110 km. In the evening, E‐fields drive downward ion motion and increase the descending EsL density and occurrence. E‐fields affect day‐to‐day EsL variations at geomagnetic mid‐latitudes by altering background metal ion distribution and transport.