Global 3-D electromagnetic forward modelling: a benchmark study

Global electromagnetic (EM) induction studies have been the focus of increasing attention during the past few years. A primary stimulus for this interest has been increased quality, coverage and variety of the newly available data sets especially from recent low-Earth-orbiting satellite missions. The combination of traditional ground-based data with satellite-borne measurements presents intriguing opportunity to attack the most challenging problem of deep EM studies: the recovery of 3-D variations of electrical conductivity in the Earth's mantle. But the reliable inference of deep-Earth electrical properties depends on the accuracy and efficiency of the underlying forward modelling solutions used to model 3-D electromagnetic induction in a heterogeneous sphere. Several 3-D forward solvers have been proposed over the last decade, which are based on staggered-grid finite difference, integral equation, finite element and spherical harmonic-finite element approaches. However, there has been no systematic intercomparison amongst the solvers. The goal of this paper is to conduct such a study in order to explore the relative merits of the different approaches when confronted with a set of synthetic models designed to probe the numerical accuracy of each. The results of the intercomparison are presented along with performance metrics to help assess the computational costs associated with each solutio

The Swarm Satellite Constellation Application and Research Facility (SCARF) and Swarm data products

Swarm, a three-satellite constellation to study the dynamics of the Earth's magnetic field and its interactions with the Earth system, is expected to be launched in late 2013. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution, in order to gain new insights into the Earth system by improving our understanding of the Earth's interior and environment. In order to derive advanced models of the geomagnetic field (and other higher-level data products) it is necessary to take explicit advantage of the constellation aspect of Swarm. The Swarm SCARF (Satellite Constellation Application and Research Facility) has been established with the goal of deriving Level-2 products by combination of data from the three satellites, and of the various instruments. The present paper describes the Swarm input data products (Level-1b and auxiliary data) used by SCARF, the various processing chains of SCARF, and the Level-2 output data products determined by SCARF