Evaluation of the applicability of the Chapman-Miller method on variation of the geomagnetic total intensity field in Taiwan from 1988 to 2007

The solar (S) and lunar (L) variations of geomagnetic fields at the horizontal (H), declination (D), and the downward vertical component data (Z) are modeled by the Chapman-Miller method with four order harmonics. In this paper, we compare S and L variations of the geomagnetic total intensity field using a consistent method with 3-component data for seasonal variations (summer, winter, and equinox) for three distinct phases during the years 1988 - 2007. The results show that consistency in the S and L variations for geomagnetic total intensity indicates normal stations and discrepancies are occurred due to data quality. In application, consistent results also prove that the function of the magnetometers at TW was normal and that large anomalies were certainly in existence during the Chia-Yi earthquake.