Dr. Florian Lhuillier receives research scholarship from Alexander von Humboldt Foundation

The geomagnetic field—mainly produced by convective motion in the Earth’s outer core—evolves in time over both historical and geological timescales. Such “geomagnetic secular variation” is directly palpable thanks to field models based on satellite and observatory data. It is however not the case for the paleosecular variation that can only be assessed by indirect proxies, an example of which comes from the scatter of virtual geomagnetic poles. We propose to identify the parameters that could best quantify paleosecular variation from real data, with the intent to identify whether different dynamo regimes indeed exist. To this end, we first propose focusing on numerical dynamo solutions that will be chosen for their Earth-likeness and integrated over a few tens of millions of years. From these solutions, we will generate synthetic data comparable in genre to real ground data, and will seek to identify the best criteria to quantify the state of the geodynamo. Once and if such criteria are identified, we will test them on real data: e.g. to say whether the state of the geodynamo is different before and after geomagnetic jerks, and between the Cretaceous normal superchron and the past five million years. Having long dynamo solutions at our disposal, this study will also be the occasion to better understand the link between short-term (historical) and long-term (paleomagnetic) secular variation.