Lunar perturbations in columnar electron content and their interpretation in terms of dynamo electrostatic fields

Both the sun and the moon exert influences on the ionosphere, causing fluctuations in its electron content. The small lunar effects, though not negligible, are difficult to analyze because their periodicities differ little from the periodicity of the dominant solar effects. A finite duration impulse response filter was perfected, permitting the efficient splitting of our columnar electron content data into a solar, a lunar, and a residual component. The solar component plus the lunar component and the solar component alone were processed by a dynamic ionospheric simulation program that yields values of vertical plasma drifts when electron content data are used as input. The difference between the two plasma drifts so obtained was taken as being the plasma drift caused by the electric field generated by the lunar tides in the dynamo region. This technique appears to be the first to allow a direct estimation of the lunar-induced electric fields in the ionosphere.