Nils Olsen

Improving the Definition of Cratonic Boundaries Utilizing the Lithospheric Magnetic Field derived from CHAMP Observations

We confirm the utility of a global non-satellite-based magnetic model of induced magnetizations in the terrestrial lithosphere by comparison in the North American region. We discuss the extension of the model to other regions, pointing out where inadequacies exist in our knowledge. Finally, we suggest some possible improvements that would make the model less subjective and more automatic.

Satellite Magnetic Residuals Investigated With Geostatistical Methods

The geomagnetic field varies on a variety of time‐ and length scales, which are only rudimentarily considered in most present field models. The part of the observed field that cannot be explained by a given model, the model residuals, is often considered as an estimate of the data uncertainty (which consists of measurement errors and unmodeled signal), and is typically assumed to be uncorrelated and Gaussian distributed. We have applied geostatistical methods to analyze the residuals of the Oersted (09d/04) field model (www.dsri.dk/Oersted/Field models/IGRF 2005 candidates/), which is based on 5 years of Orsted and CHAMP data and includes secular variation and acceleration, as well as low‐degree external (magnetospheric) and induced fields. The analysis is done in order to find the statistical behavior of the space‐time structure of the residuals, as a proxy for the data covariances. Once these are known, they can be used in the modeling process to improve the model, estimate its uncertainty, and eventual...

Magnetic Crustal Thickness in Greenland from CHAMP and Ørsted Data

The magnetic crustal thickness of Greenland and the surrounding area is determined by inversion of gridded values of the magnetic radial component as given by the IDEMM model, which is based on CHAMP and Orsted data alone, and by the Comprehensive Model (CM4), which is based on satellite and observatory data.