The importance of electric field in ions convergence and formation of sporadic E (Es) at the equatorial region

The importance of electric field in formation of sporadic E (Es) at the equatorial region is investigated both analytically and numerically. In the suggested theory, the electric field in the lower thermosphere of the equatorial region is competitive to the effects of neutral wind direction, value and shear on ions vertical convergence into Es type high density thin layer. We show analytically that minimal negative values of vertical changes of the ions vertical drift velocity, which are necessary for ions convergence into a Es type layer, is possible due to electric field. 

We also noted the importance of the electric field value and direction (including its components) in formation of the sporadic E. The electric field, even it is homogeneous in the region of ions convergence, can cause ions convergence into a Es type thin layer. The possibility of formation of the Es layer is demonstrated numerically in cases of presence of electric field with the zonal components.   

We used the HWM14 data which also showed the importance of competitive effects of the electric field and neutral wind velocity in formation of the Es layers. Here it is also noted the decrease of the electric field effect and increase of the neutral wind (including zonal and meridional winds) factor from equatorial to mid-latitude regions. 

The electric field also has an influence on the competitive roles of itself and the neutral wind in ions divergence. In the suggested theoretical model, the arbitrary wind velocity profile (including the vertical component), caused by atmospheric waves, can be taken into account. The possibility of theoretical prediction of the ions convergence/divergence processes at the regions, where they develop, shows that it is important to investigate the global distribution of molecular and heavy metallic ions in the lower thermosphere.