Asymmetry of the TEC Anomaly from the Meridional Neutral Wind and Equatorial Electrojet Perspectives

Abstract:

The equatorial ionization anomaly (EIA) is significant ionospheric phenomena caused by the so-called fountain effect, which is driven by a zonal eastward electric field. This process involves the altitudinal coupling, electrodynamics and inhomogeneity of ionospheric plasma densities in the equatorial and low latitude regions. Not only eastward electric field, but neutral winds also play a role in controlling the actual configuration of the EIA. In the present study, an attempt is made to reveal the effect of the longitudinal variability of the equatorial electrojet (EEJ) strengths associated with eastward electric field and meridional neutral winds for the generation and control of the asymmetries on EIA crests of TEC (Total Electron Content) about the magnetic equator in the American sector. Our results show that as EEJ is stronger (weaker), EIA crests are formed farther (closer) from equator on the western (eastern) side of South America. A physics-based numerical model is used to study the effects of daytime meridional neutral winds and EEJ on consequent evolution of asymmetry in equatorial TEC anomalies during afternoon and onwards. This result implies that the electric field associated with the EEJ together with meridional neutral winds may play a key role in the development of observed asymmetries of EIA crests and dictate the shape, size, amplitude and separation of the EIA crests as seen through ionospheric TEC distribution measured using GPS (Global Positioning System) in the low latitudes ionosphere.