Theoretical models of ionospheric storms

Summary Precipitations of soft particles at the polar region will enhance the electron density in the oval shaped region surrounding the pole and their effects are marked at winter night.Reduction in the electron density in the sunlit polar region and at the trough may be caused by polar atmospheric heating through two processes; one is the increased chemical reaction coefficients controlling the loss rate of electron density and the other is the decrease in atmospheric density ratio O/N₂ near the turbopause caused by enhanced mixing by atmospheric gravity waves or by convective motion of the upper atmosphere.Positive disturbances of the ionosphere appearing in the evening or around noon at mid-latitudes on the storm developing stage, may be caused by equatorward meridional wind arising from a pressure gradient in the upper atmosphere, though the effects of electric fields cannot be ruled out.The Dst part of ionospheric storms persisting over several days may be caused by changes in atmospheric composition arising from global convective motion of the upper atmosphere.Equatorial ionospheric storms are probably caused by changes in east-west electric fields in the equatorial ionosphere arising probably from disturbance electric currents flowing at the polar region.