Project Details
Projekt
Global time-averaged reconstructions of the geomagnetic field through deep geological times and their implications on the Earth's deep interior
Applicant
Dr. Sanja Panovska
Subject Area
Geophysics
Term
since 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 521548146
Studying the geomagnetic field variations throughout geological history is essential for understanding the dynamical processes in the Earth’s outer core and coupling with other layers. Reconstructions of these long-term variations are only possible when sufficient data are available for a given time period. Recent progress in compiling paleomagnetic data resulted in a database that contains paleomagnetic intensity and directions since 4 billion years ago (named PINT). The aim of this project is to build global, time-averaged field (TAF) models covering selected time intervals over the Earth’s history. Of particular importance are periods when the field was stable for a very long time, such as the Cretaceous Normal Superchron, or very active, for example, the Jurassic Hyperactive Period, as well as different epochs considering all data, and normal and reversed separately. Besides the spherical harmonic representation, a method for estimating localized spatial averages of the radial field at the core-mantle boundary (CMB) will be applied. The method also provides model variance and resolution kernels, which allow for a better appraisal of what can be resolved from the data. Further tests will be provided by considering different selection criteria if enough sites for global TAF models are available. One critical issue that needs to be addressed is the paleospatial data distribution. A few different plate motion models will be used to reconstruct the site original locations in order to obtain robust TAF estimates. The following challenge is to incorporate the data location errors in the inversion, and one approach will be to translate these uncertainties into measurement errors. The main objectives of the projects are 1) to identify persistent anomalous features of the geomagnetic field at the Earth’s surface and the CMB; 2) to investigate the differences and similarities of stable/unstable fields; 3) to check for recurring features compared to the present-day field, like the South Atlantic Anomaly; 4) to assess the field asymmetry in both spatial and time scales; and 5) to test the relationship to features in the deep Earth. For the latter, because the variations observed on these long timescales (tens to hundreds of millions of years) are similar to the timescales of mantle convection, their linkage may shed light on the lowermost mantle convection processes.
DFG Programme
Priority Programmes
