Abstract
Abstract 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.
Highlights
The main geomagnetic field changes both spatially and temporally
Main field and secular variation can be obtained with spatial-temporal models such as the International Geomagnetic Reference Field (IGRF)
We proposed a regional spatial-temporal model of the geomagnetic field to estimate the secular variation in Japan
Summary
The main geomagnetic field changes both spatially and temporally. In order to investigate the spatial distribution of the main field in Japan, the Geographical Survey Institute (GSI) carried out the measurements at first- and secondorder geomagnetic stations. The magnetic charts provide accurate geomagnetic field values for Japan and are widely used as a reference for the study of local geomagnetic anomalies in this region. They give no detailed information about the secular variation since the charts are produced every ten years (tenyear resolution) only. Main field and secular variation can be obtained with spatial-temporal models such as the International Geomagnetic Reference Field (IGRF). In order to obtain a precise model, we develop a regional secular variation model
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