The lunar geomagnetic tide at night

Abstract

Hourly values from 1964–65 of the three geomagnetic elements from a large number of stations have been analysed for the various lunar components. These were combined to examine in detail the seasonal and diurnal variations of the lunar geomagnetic tide at night. Comparison of the values for the oceanic component calculated in a similar way to Malin (1973) showed good agreement between sunspot maximum and minimum years. When seasonal changes were included, the D and Z elements gave evidence of a lunar modulation of magnetic field aligned currents entering the ionosphere in auroral regions. The effects of these currents appeared to extend as far away as the equator. Changes in their amplitude during the night also suggest a relation to auroral processes. There is a just‐resolved nighttime equatorial electrojet H component and a quite large lunar H component in the auroral regions. Copyright © 1987, Wiley Blackwell. All rights reserved