Secular variation of Geomagnetic Elements at Alibag-

Abstract

Attempts are made to represent secular variations of geomagnetic elements (H. Z and D) of Alibag by fitting polynomials of third order to the observed annual mean values for the years 1905-65. The coefficients of the fitted curve account for more than 99 percent of the total variation in case of H and D and 98 per cent in case of z. The coefficients are compared with those computed by Moos, Pramanik and Pramanik and Ganguli for the same station. A probable change of  position or intensity or both of the focus of the H-field in the region is inferred from the change in trend of H and D curves about the year 1964. The residual H,Z and D curves did not show any parallelism with solar activity as judged from sunspot numbers. H and Z residuals nearly indicated a periodicity of 3 solar cycles whereas D showed a periodicity of 2 solar cycles.