HR: 08:45h
AN: GP31A-04    [Abstracts]
TI: Modelling the secular variation at a regional scale
AU: * Thebault, E
EM: ethebault@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, Place Jussieu, Paris, 75252, France
AB: In the recent years, several modelling techniques were proposed to represent the magnetic field at a regional scale using ground, aeromagnetic and satellite data. The Revised Spherical Cap Harmonic Analysis (R-SCHA) is suitable for representing the data measured at different altitudes. However, it has always been numerically challenging to represent the three components of the magnetic field with data measured on a single surface because a 2D constrain is not sufficient to uniquely solve a 3D problem. In this paper, we address this previous drawback. The new solution of Laplace equation, named R-SCHA-2D, is expressed in terms of associated Legendre functions and a special case of Conical functions that form a complete block-orthogonal basis function on a spherical cap domain. The efficiency of this modelling will be first demonstrated on a set of synthetic data and compared with the standard Spherical Cap Harmonic Analysis (SCHA). In a second step, we perform a spatio-temporal modelling of the french repeat stations data between 1960 to now using temporal splines and R-SCHA-2D functions. We finally compare the regional model with global IGRF secular variation prediction and we discuss the consistency of the obtained small-scale secular variation features over France.
DE: 1532 Reference fields: regional, global
DE: 1545 Spatial variations: all harmonics and anomalies
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting