The Study of Magnetic Field Models for Philippines and Its Neighboring Regions

According to the magnetic field data on 74 survey sites, which was measured in the Philippines during 2001~2007, using two methods of spherical cap harmonic and Taylor, we established the magnetic field model on 2005.0 epoch for Philippines and the surrounding regions and got the distribution of the seven components of X,Y,Z,D,I,H, and F. The distribution is similar in the two models, the difference is the relief of inflection point and contour smoothness. At about 8ºN, X, H, and F have turning points and are higher in west than in east. The D and Y zero lines are distributed at 8ºN, the northern part of the line side is negative and the southern part is positive, while the distribution of the contours is along the longitude direction, and exist gurgitation along latitude direction. The distribution of Z and I is more regular, of which the zero‐line distribution is at the 7.5ºN. The value is positive in the northern region and negative in the southern regions. The difference between the two models from the IGRF distribution patterns are very different. The value of the spherical harmonic model minus the IGRF model reveals a feature of positive and negative phase, and the maximum value of each component abnormal distribution of positive and negative values is at low latitudes. The abnormal distribution of Taylor minus IGRF is more complete.