Variaciones geomagneticas diarias debido al efecto lunar: estudio basado en datos del observatorio geomagnetico de Huancayo

The Moon apparently seems to have not appreciable effect in the geomagnetic monthly period, but Keil (1839), Sabine (1853), Broun (1874) and many others have shown a lunisolar daily variation. It is known that solar (S) and lunar (L) variation have seasonal variations. Seasonal changes of S, particularly on quiet days, have been studied in greater detail than the seasonal changes for L. The purpose of this paper is to describe in more detail the effect of the variation of L in the geomagnetic equator, in the absence of strong perturbations selecting conveniently geomagnetic data of Huancayo observatory (hourly mean) from January 1, 2008 to December 31, 2009, period which is longer in range of minimum solar activity of the last 160 years (end of solar cycle 23 and start of solar cycle 24). The spectral analysis by wavelet and Fourier allows us to identify the main contribution of S diurnal and semidiurnal variations and its sidebands, besides the effect of the seasonal variation. In order to observe the variation L is subtracted the variation S together with its sidebands, allowing observed by Fourier spectral analysis and wavelet as the main contributions to the variation L, similar effect were described by Chapman and Miller (1940).