High resolution geomagnetic spectra in Indian region: lunar tides

Abstract

A search for major and minor lunar geomagnetic tides in the Indian region is made from high resolution power spectra, obtained by the Maximum Entropy Method (MEM), at two low latitude stations. The results indicate, on the basis of frequency comparison, that only near the dip equator is there clear evidence for the lunar tidal mechanism being the dominant factor over the amplitude modulation mechanism. Amplitudes of the lunar terms near 1 and 2 c day^-1 show equatorial enhancement with greater enhancement for the semidiurnal terms. The lunar semidiurnal term, M₂, shows the largest enhancement.