Numerical Study Of The Ionospheric Electric Field At Mid- And Low Latitudes And It's Influence On The Ionospheric Annual And Semi-annual Variations

It is well known that the ionospheric electric fields and currents play important roles in the ionosphere electrodynamics. Although we have many means to sound the ionospheric fields, such as VHF radars, incoherent scatter radars, rockets and satellites, we still have very limited knowledge about them. Numerical simulation is a new method of studying the ionospheric electric fields, which make it possible for us to investigate the electric fields and currents in more detail and for more convenience. On the other hand, data analysis reveals that the ionosphere and its background thermosphere undergo numerous kinds of variations, i.e. the diurnal, day-to-day, semiannual and annual variations. As for the semi-annual and annual variations of the electron density, there are many theories to explain, such as the geometrical, thermal and chemical explanations. Although these theories can explain the variations to more or less extend, but still remain puzzles. Especially in the equatorial region, it is well known that the'foundation effect'caused by the electric fields control many phenomena in the ionosphere. So we wonder that to what extent the electric fields can influence on the semi-annual or annual of the ionosphere. Therefore, the major works in this paper has been carried out in the following aspects, (1) establishing a theoretical electric fields model to study the morphology and structure of the ionospheric electric field, current et al., (2) data analysis the annual and semi-annual variation of the global observed NmF2 as well as the TEC, (3) modeling and explaining the yearly variation of the electric fields in the equatorial ionosphere, (4) using an ionospheric model to investigate the predominant semi-annual variation of NmF2 in the equatorial ionosphere.(1) In the first section of this paper, we developed a theoretical model for ionospheric electric fields at mid- and low- latitudes. Under the geomagnetic dipolar coordinate system, a partial differential equation of electric potential is deduced from the ionospheric dynamo theory and taken as the fundamental equation for the electric...