抄録
Geomagnetic data from twelve stations have been analyzed for O1 lunar tidal variations by the Chapman-Miller method. Well-determined geomagnetic O1 tides were found in the vertical component at several stations. In most cases little or no solar modulation of the fundamental frequency of the O1(Z) tide was detected, thus making an ionospheric source for the O1(Z) tide unlikely. The most probable cause of the O1(Z) variation is electric currents induced in the oceans by O1 tidal currents. No definite conclusions could be drawn about O1 tides in the horizontal component of the field because of ambiguity between genuine O1 tides and seasonal changes in the M2 geomagnetic tide.
