EFFECT OF SEA ON LUNAR VARIATIONS OF VERTICAL COMPONENT OF GEOMAGNETIC FIELD

A number of observatories, mostly near the coast, show an anomalous value for L2(Z) which is probably caused by tides in the sea. In an attempt to separate the sea tide and ionospheric effects, data for the IGY have been analysed treating day and night separately. The night-time values are ascribed to non-ionospheric causes, and are used to produce a 'corrected' L2(Z) of purely ionospheric origin. Although the 'corrected' values are much smaller than the uncorrected values, they show a much more consistent pattern. The nonionospheric effect is much larger than had been suspected and appears to extend for a considerable distance inland. © 1969.