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Preliminary investigation into the lunar semidiurnal variation in the magnetic elements at Cape Town and Hermanus

1963; American Geophysical Union; Volume: 68; Issue: 7 Linguagem: Inglês

10.1029/jz068i007p02061

2156-2202

A. M. van Wijk, Hugh Bergh,

Scientific Research and Discoveries

Because of the moon's tidal action on the earth's atmosphere, ionized gases are drawn across the lines of force of the earth's magnetic field. Electric currents thus induced in the ionosphere cause variations in the geomagnetic field which are superimposed on much larger solar and irregular variations. Computation of the lunar effect thus necessitates the use of data covering a long period. Results are here presented of a preliminary investigation into the lunar semidiurnal variation in the magnetic elements at Cape Town (1933-1940) and Hermanus (1940-1950). This investigation was instigated by one of the authors (AM.v.W.) in connection with the elimination of non-K variations from the Hermanus K indices. Most of the computations were carried out by the late B. Gotsman, and the work was discontinued after his death in 1958 owing to shortage of computing staff at the Hermanus Magnetic Observatory.