HR: 11:05h
AN: GP21D-04 INVITED     [PDF]
TI: Improving the Resolution of the Lithospheric Magnetic Field From CHAMP and Upcoming SWARM Satellite Measurements
AU: * Maus, S
EM: smaus@gfz-potsdam.de
AF: GeoForschungsZentrum, Telegrafenberg, Potsdam, 14473 Germany
AB: Continental scale magnetic anomalies contain unique information on the structure and composition of the largely inaccessible lower crust. The new satellite magnetic missions provide the opportunity to see these anomalies in unprecedented clarity. Current anomaly maps extend to spherical harmonic degree~80, corresponding to wavelengths of about 500~km. This leaves an uncovered waveband between satellite maps and aeromagnetic compilations, which become unreliable at wavelengths exceeding the dimensions of the individual surveys, typically of the order of 100~km. Revived efforts to combine satellite and aeromagnetic data to a world magnetic anomaly map require information in the intermediate waveband. Narrowing this gap is an important motivation for further improving the resolution of satellite magnetic anomaly maps. A comparison of individual CHAMP repeat tracks shows consistent crustal features with wavelengths smaller than 500~km. To map such features requires very clean data. Since mid latitude and polar data have very different behaviour, we treat them as separate (overlapping) data sets. Apart from the usual main and external field corrections, we fit and subtract internal and external dipoles to remove long wavelength magnetospheric and induced fields. Furthermore, we fit and subtract the far-ranging effect of polar electrojets from the mid-latitude data. In the polar caps we use only the most quiet tracks, rejecting 95~% of the data. Having once identified the magnetic signal of ocean tides, we now subtract model predictions of the major tidal constituents in order to further reduce noise levels. In particular, this improves the levelling of adjacent tracks which is essential for retrieving the East/West signal. Our immediate aim is to produce a reliable anomaly map to degree~90. A further boost in resolution and accuracy is expected from the upcoming multiple satellite SWARM mission. We currently investigate optimum orbit constellations in an end-to-end mission simulator.
UR: http://www.gfz-potsdam.de/pb2/pb23/SatMag/model.html
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1532 Reference fields (regional, global)
DE: 1545 Spatial variations (all harmonics and anomalies)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting