A Theoretical Model Of Low-Latitude Ionospheric Electric Field

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 limited knowledge about it. 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.In this paper, a theoretic model of low-latitude ionospheric electric field is established. The model is based on the ionospheric dynamo theory. On the center dipole magnetic field coordinate, the dynamo equation is deduced into anelliptical partial differential one. By spectral method we can solve this equation successfully.In this numerical model, three-dimension structures of electric potential, fields and currents in the ionosphere have yielded. Since many people have been attracted to study the equatorial electrojet, and considerable progresshave been accomplished in the understanding of these phenomena, we focuson the vertical structure and meridinoal profile of the equatorial electrojet. After a comparison with some observed dates and calculated results of other authors, we can consider this model as a reliable one.The modeling of electrojet indicates as follow.(1) Electric charges can be found due to the inhomogeneous structure of polarization electric field and conductivity.(2) The electrojet is distributed within a narrow region along magnetic latitude and height. At daytime the electrojet is primarily eastward, while at nighttime the electrojet is primarily westward. Inmost periods, vertical structure of currents density is dominant by the feature of a peak on 120-km height, and the second density peak usually can be found nearby. The occurrence of reverse current at litter higher latitude than equation is very commonplace between the time of afternoon and sunset. (3) When integrate horizontal currents from the height of 90 kmto 400k m, an obviously counterclockwise vortex can be found. Compared it with Sq current system, we find that the characteristics of height-integrated horizontal currents agree with Sq current system very well.