In 2022, the Senate of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) established the Priority Programme, Reconstructing the Deep Dynamics of Planet Earth over Geologic Time (DeepDyn) (SPP 2404). The programme is designed to run for six years. The official call for individual proposals was published on 27 June 2022 for the first three-year funding period.

One of the most striking properties of the geodynamo are complete reversals of the dipole field. The reversal frequency changes over geologic time scales typical of mantle convection. Numerical simulations indeed indicate that the lower mantle has a manifold impact on the dynamo where the absolute value and pattern of the heat flux through the core-mantle boundary affects the field strength, field geometry and reversal rate. However, neither the long-term evolution of the lower mantle and the dynamo, nor the coupling between the two are well understood, which forms the basis of DeepDyn.

To reconstruct the long-term evolution of the Earth, DeepDyn aims to understand how the iron core, stratified layer, and rocky mantle interact and how material properties affect the processes. Moreover, geomagnetic field strength and reversal rate likely influence the survival and evolution of magnetoreceptive organisms, especially magnetotactic bacteria. Magnetofossil records may therefore provide important additional information on the ancient geomagnetic field that complements paleomagnetic data.

To tackle this highly integrated project, 23 individual proposals have been funded that fall within five overriding themes: (1) reliable paleomagnetic data and geomagnetic models and (2) state-of-the-art dynamo simulations that together provide information on the evolution of the core dynamo; (3) realistic mantle evolution reconstructions over >10 Myr time scales that provide essential boundary conditions for the long-term core dynamics; (4) robust estimates of core and mantle structure and properties that determine the parameters of core and mantle dynamics; and constraints on geomagnetic field evolution from (5) magnetotactic species (biomagnetism).

Research themes within the goals of DeepDyn aim at understanding the long-term evolution of Earth’s deep interior, for example :
• The dynamics of and interaction between core and mantle
• The changes in magnetic reversal frequencies and superchrons
• The characteristics of field reversals
• The composition, structure and properties of the lower mantle and core
• Effects of stratified layers, CMB topography and inner core growth on core dynamics
• The influence of time-varying magnetic fields on the adaptation and evolution of magnetotactic species and the preservation of magnetofossils in the rock record