The effect of electric fields on the F-region behaviour as compared with neutral wind effects

Abstract

Numerical solutions of the coupled ion and electron continuity equations, ion and neutral dynamical equations, and ion and electron heat conduction equations are used to determine the relative importance of neutral winds and electric fields in the diurnal behaviour of the F-layer. The main results, derived for the midlatitude ionosphere at equinox and medium solar activity, are: 1. (1) The W-E electric field giving about the same effect in F-layer as a N-S wind based on Jacchia's model has a maximum of 7 V/km at 0200 hr and a minimum of −5 V/km at 1800 hr. 2. (2) At night, the total vertical electron-ion velocity above 300 km is about zero. 3. (3) Above 300 km, therefore, the electron-ion velocity along the magnetic lines of force is proportional to the W-E electric field strength E y . Vasseur's measurements indicate that E y is smaller than 2 V/km at night. 4. (4) Ion temperature measurements with the incoherent back-scatter technique give a much larger temperature amplitude than assumed in Jacchia's model. If we modify Jacchia's model correspondingly, we obtain an unrealistically large rise of the F-layer height at night. The electric W-E field that would suitably reduce the height rise is much larger than permitted by Vasseur's results. The solution to this problem seems to lie in introducing variable lower boundary conditions in the atmospheric model.