Longitudinal and seasonal structure of the ionospheric equatorial electric field

Abstract

[1] The daytime eastward equatorial electric field (EEF) in the ionospheric E-region plays an important role in equatorial ionospheric dynamics. It is responsible for driving the equatorial electrojet (EEJ) current system, equatorial vertical ion drifts, and the equatorial ionization anomaly. Due to its importance, there is much interest in accurately measuring and modeling the EEF. In this work we propose a method of estimating the EEF using CHAMP satellite-derived latitudinal current profiles of the daytime EEJ along with Δ H measurements from ground magnetometer stations. Magnetometer station pairs in both Africa and South America were used for this study to produce time series of electrojet current profiles. These current profiles were then inverted for estimates of the EEF by solving the governing electrostatic equations. We compare our results with the Ion Velocity Meter (IVM) instrument on board the Communication/Navigation Outage Forecasting System satellite. We find high correlations of about 80% with the IVM data; however, we also find a constant offset of about 0.3 mV/m between the two data sets in Africa. Further investigation is needed to determine its cause. We compare the EEF structure in Africa and South America and find differences which can be attributed to the effect of atmospheric nonmigrating tides. This technique can be extended to any pair of ground magnetometer stations which can capture the day-to-day strength of the EEJ.Citation: Alken, P., A. Chulliat, and S. Maus (2013), Longitudinal and seasonal structure of the ionospheric equatorial electric field,

Longitudinal Variation of the Lunar Tide in the Equatorial Electrojet

“…The polarization electric fields generated in the E region are transmitted to the equatorial F region (>150 km) along equipotential magnetic field lines. These electric fields are usually eastward during daytime, and thus, at the magnetic equator where the geomagnetic field is horizontal, plasmas are transported vertically upward by the E × B drift (Alken, Chulliat, et al, ; Fejer et al, , ). The lifted plasmas eventually diffuse downward and poleward along the geomagnetic field lines and produce the so‐called equatorial anomaly crests at approximately ±15° from the magnetic equator (Hanson & Moffett, ; Moffett & Hanson, ).…”

Lunar-solar interactions in the equatorial electrojet

“…These as well as more recent studies focus on such phenomena as lunar and solar tide‐driven variability [e.g., Lühr et al , ; Lühr and Manoj , ], the reverse electrojet [e.g., Vineeth et al , ], planetary wave signatures [e.g., Parish et al , ; Abdu et al , ], correlations with solar flux [e.g., Briggs , ], and relationships with sudden stratosphere warnings [e.g., Park et al , ]. In the most recent decade, space‐based observations of magnetic field variability have enabled studies that delineate the longitudinal variability of the electrojet [e.g., Lühr et al , ; Alken et al , ].…”

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

“…The corrected hourly data are V t = V t − Qt ; so that V 0 = V 24 . Alken et al (2013) used cubic splines, instead of linear regressions, in order to represent the non-cyclic variation. They first fitted the cubic splines to the nighttime data (2200 to 0500 LT) and then subtracted those fits from all the data.…”