Ion Drag with Electrodynamic Drift; a Computer Experiment for the F2 Layer

Summary The model F2 layer considered is one in which the ions move under the influence of electrodynamic drift and simultaneously diffuse along the geomagnetic field lines. Both these motions are assumed to set the neutral air moving horizontally. The problem is made soluble by assuming that the ratio b of the horizontal velocity of the neutral air to the horizontal velocity of the ions is constant. Thus b = 0 corresponds to a stationary neutral atmosphere, while b = 1 corresponds to the case of fully matched horizontal velocities. Allowance is made for curvature and convergence of the (dipole) magnetic field lines, and for variations of electron density with latitude and height. The model layer is isothermal, and is made symmetrical about the equator by assuming that the geomagnetic dipole axis coincides with the Earth's axis of rotation. Equilibrium is assumed; thus the calculations hold only for some fixed time in the early or middle afternoon. The results show that the value chosen for b chiefly affects the overall magnitude, rather than the distribution, of electron density. Electrodynamic drift is much more important than ion‐drag in determining the distribution. The calculations therefore support others made recently, which confirm Martyn's theory that electrodynamic lifting is a major feature of the low latitude ionospheric F2 layer. However, the motion of the neutral air in this particular model does have some effect. The results are discussed in relation to other theoretical and experimental work.