Earth Planets Space, Vol. 58 (No. 6), pp. 757-763, 2006
Xiaoli Ji1, Mitsuru Utsugi2, Hiroki Shirai1, Akira Suzuki1, Jinlan He1, Satoshi Fujiwara1, and Yoshihiro Fukuzaki1
1Geographical Survey Institute, Kitasato-1, Tsukuba, Ibaraki 305-0811, Japan
2Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Kawayo, Minami-Aso, Kumamoto 869-1404, Japan
(Received April 28, 2005; Revised August 9, 2005; Accepted August 16, 2005; Online published June 2, 2006)
A geomagnetic regional model is constructed to provide a spatial-temporal variation of three orthogonal components (X, Y, Z) in Japan. In order to obtain a high temporal and spatial resolution, Natural Orthogonal Components (NOC) analysis and Spherical Cap Harmonic (SCH) analysis were employed to produce a spatial-temporal model based on the observed data from geomagnetic observatories and continuous geomagnetic stations. Using this model, we calculated the secular variation between 1999 and 2004 in Japan. The root mean square (RMS) scatter of the model is less than 3 nT, which indicates a good agreement between calculated and input data.
Key words: Geomagnetic regional model, spatial-temporal model, secular variation, Natural Orthogonal Com-ponents, Spherical Cap Harmonic.