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SHA vs. SCHA for Modelling Secular Variation in a Small Region Such as Italy

A. De Santis, C. Falcone, J. M. Torta
1997 Journal of geomagnetism and geoelectricity  
The possibility of obtaining a reasonable analytical model ofthe geomagnetic field secular variation (SV) in a space-time window limited to the measurements taken in Italy from 1965 onwards is discussed. The main purpose of the work is to provide a mathematical representation better for the small Italian region than the International Geomagnetic Reference Field (IGRF) which is formulated on a global scale. With this aim regional models constructed in polynomial form already exist, but they do
more » ... xist, but they do not account for the physical constraints imposed by Laplace's equation. Spherical cap harmonic analysis (SCHA) is shown not to be suitable for SV modelling over such a small region and the final adopted model is essentially a conventional spherical expansion. It is demonstrated that it is possible to find a solution to our inversion problem that fits the data by using a limited number of harmonics, selected on the basis of significance using a regression procedure.
doi:10.5636/jgg.49.359 fatcat:l5eo24t47jemzooistajyuq3qy