Equatorial geomagnetic anomaly and its associated current system

Abstract

From a detailed study of the momentum transport equation for charged gaseous fluids moving through a neutral gas, it is suggested that the equatorial F‐region electron‐density distribution (the geomagnetic anomaly) is simply the natural steady‐state distribution one would expect for charged fluids under the influence of gravitational, electric, and magnetic fields and production and loss, when interaction with the neutral medium is negligible. It is shown that this steady‐state distribution maintains itself by means of a longitudinal current system, and a study of the properties of this longitudinal current system leads to a technique for its complete mapping in the upper F region of the ionosphere. Quite importantly, it is shown that the latitudinal electron‐density distribution that characterizes the equatorial anomaly cannot exist when the longitudinal current system is absent. The study of the longitudinal current system also demonstrates the possibility of large errors in temperature calculations that utilize vertical density slope measurements to determine scale height, and a technique is suggested to correct such calculations. Finally, using cited measurements for support, it is possible to suggest the mechanisms responsible for the diurnal and asymmetric behavior of the anomaly.

Electron concentration variations in the topside ionosphere between 60°N and 60°S geomagnetic latitude associated with geomagnetic disturbances

“…Owing anomaly in the topside ionosphere was dis-to this movement, concentrations in the lower cussed by King et al [1964] and Lockwood and topside ionosphere (from the height of F-region Nelms [1964]. Formation theories of the equa-peak to about 600 km) become less than those torial anomaly maximum and minimum were in the case of no drift, and the height of the presented by Martyn [1955], Duncan [1960], maximum concentration rises slightly, but not Goldberg andSchmerling [1962, 1963], Rish-greatly, because the electron production due beth et al [1963], Lyon [1963], Chandra to photoionization continues during electron [1963,1964] .it a slightly higher latitude than the magnetic equator, the electron drift is perpendicular to the geomagnetic field lines, that is, upward and northward in the northern hemisphere. The reduction in electron concentration in the lower topside ionosphere due to this drift takes place in the same way as at the equator, although at a slower rate.…”

Ionospheric midlatitude electric current density inferred from multiple magnetic satellites

“…The two parts of the second term in equation describe the gravity and pressure gradient electric currents, respectively. Rishbeth [] described the electric forcing, while Goldberg [] discussed the gravity and pressure driven currents (neglecting the effect of neutral air winds). While the ionosphere as a whole can reasonably be defined as horizontally stratified, the electrodynamic coupling of the E and F regions produces complex structure and marked meridional gradients in the plasma distribution, thus affecting the distribution of electric currents.…”

On explaining the behavior of the ionospheric F region

“…A more detailed study shows that other motions exist that •re generally smaller th•n the pl•sm• velocity but unequal for electrons •nd ions, so that sm•11 electric currents flow. The •mpere force produced by these currents plays •n essential role in the equilibrium of the pl•sm• [Chandra a•d Goldberg, 196•;Ferraro 196•;Gladdon, 1965;Goldberg, 1965;Kendall, 196•], but, since the currents •re •lmost divergence free, they do not •ppear directly in the transport term of the continuity equation (1). [Hinteregger, 1965;Aller•, 1965].…”

“…[Martyn, 1947[Martyn, , 1955]. A refers to the apex of the field line, that is, [Goldberg, 1965] and with the transport of plasma along field lines required by theories such as Martyn's. But since these calculations need to assume the variation of Nx with height at the equator, they do not lead to any physical explanation of the equatorial anomaly.…”