Geodynamics Science Highlight NASA GSFC Geodynamics 921

SCIENCE HIGHLIGHT

Geodynamics Branch, Code 921

SEPTEMBER 2003

Comprehensive Magnetic Field Model Finds Many Fans, Many Uses
Sabaka and Model in Heavy Demand for a Variety of Applications

Terry Sabaka (Raytheon STX and Geodynamics Branch) is a principle architect of the GSFC/DSRI magnetic Comprehensive Model (CM). This model uses satellite and surface data to simultaneously represent the contributions from the core, crust and external (ionospheric and magnetospheric) fields. It is the state-of-the art description of the near-Earth magnetic field. And it is finding many fans and a wide variety of uses in the community. The figure (right) shows one example: merging local aeromagnetic surveys done at different times and at different altitudes. Former attempts using simpler global field models resulted in disconnects across survey boundaries. But Ravat and co-authors show in a recent “The Leading Edge” article, the CM’s superior representation of the changes in the Earth’s field greatly improves the ability to stitch such surveys together. The model is available in web-based form. Improvements continue, and the most recent version, CM4, was recently submitted for publication.

Figure shows aeromagnetic surveys combined using standard IGRF model and
the Comprehensive Model. From Ravat et al (2003)

Figure shows aeromagnetic surveys combined using standard IGRF model (a) and the Comprehensive Model (b). From Ravat et al (2003).

The CM has been and is now being used for:

Main field and secular variation input for the DGRF 1995, DGRF 2000 and PGRF 2005 magnetic reference fields

Leveling temporally and spatially disjoint aeromagnetic surveys by accurate interpolation of the core secular variation

Isolating portions of the field (e.g., the lithospheric field) for specific study

For calibration of SAC-C magnetometer using Oersted and CHAMP data

Isolating induced signals in satellite magnetic data to study global electrical conductivity.

Uses to which the CM will be put in the near future include:

Removing diurnally varying primary and induced magnetic fields from the upcoming planned USGS High Altitude Magnetic Map aeromagnetic data.

As the forward synthesis module in a mission simulation package supporting the SWARM constellation mission, a four satellite magnetic mapping constellation, currently undergoing an ESA Phase A study.

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Contact: Terry Sabaka, GSFC, Code 921 (sabaka@geomag.nasa.gov)

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Responsible NASA official: Dr. Herbert Frey