HR: 1340h
AN: GP33D-1602    [Abstracts]
TI: On the Comparison Between SCHA and R-SCHA Regional Modelling Techniques When Inverting Multilevel Magnetic Data Sets
AU: Gaya-Pique, L R
EM: gaya@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris - CNRS, Equipe de Geomagnetisme, 4 Place Jussieu, Tour 14/15, 2eme etage, Paris, 75005, France
AU: * Thebault, E
EM: EThebault@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris - CNRS, Equipe de Geomagnetisme, 4 Place Jussieu, Tour 14/15, 2eme etage, Paris, 75005, France
AB: Spherical Cap Harmonic Analysis (SCHA) has become a common tool for the regional modelling of potential fields since its introduction twenty years ago. The fact that the solutions provided by the technique satisfy Laplace equation, and the possibility of representing high-frequency fields with a small number of coefficients (compared to the global Spherical Harmonic Analysis) made of SCHA the preferred choice for the development, for example, of magnetic field models at national scale. However, Thebault et al. (2006) demonstrated that the traditional SCHA introduced by Haines (1985) presented some deficiencies, in particular related to the inversion of multilevel data sets. The authors presented the R-SCHA technique as an alternative method in which the introduction of a new set of basis functions and boundary conditions solved this issue. Perhaps due to the short lapse of time since the presentation of R-SCHA, the scientific community continues however to apply the classical SCHA approach when developing regional models using a blend of satellite and ground data. In this paper we present some comparisons between the SCHA and R-SCHA techniques applied to synthetic data computed using the shorter wavelength part of MF5 model at 0km, 400km, and 700km altitude, and also to a subset of the near-surface crustal field grid from the World Digital Magnetic Anomaly Map Project (WDMAM). The different tests show how R-SCHA is able to produce a consistent set of gauss coefficients avoiding the problems related to the traditional SCHA inverse problem, and how the R-SCHA model fits the radial variation of the field in a realistic way. These results should help the scientific community to evaluate the level of approximation accepted for the development of regional magnetic field models in the era of the Swarm multi- satellite mission.
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 1532 Reference fields: regional, global
DE: 1541 Satellite magnetics: main field, crustal field, external field
DE: 1545 Spatial variations: all harmonics and anomalies
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting