A regional geomagnetic model using fourier analysis

Abstract

We have Fourier analysed the horizontal component (H) of the Earth’s magnetic field at Thiruvananthapuram (lat. 8o 29’ N, long. 76o 59’ E) during the years 1987 to 1998. The infinite number of terms in the Fourier expansion was truncated after the fifth term for both magnetically “quiet” and “disturbed” days. We find that terms up to order 5 are sufficient to model the observed magnetic field at Thiruvananthapuram during both magnetically quiet and disturbed days, as there is an excellent agreement between the observed and the Fourier analysed and reconstructed fields. The seasonal and solar cycle dependence of the Fourier amplitudes have also been studied; we find the Fourier amplitudes are well correlated with the sunspot numbers.