Evaluation of archaeological and pleistocene magnetic field models and their common features

Archeo- and paleomagnetic field models show a wide range of temporal variability and of spatial content. While the temporal variability may reflect true geomagnetic field variation, the different spatial content of individual models could be explained by different modeling strategies and data sources, but most likely by data uncertainties. To overcome these problems, we derive a time-dependent mean, median and robust Huber models over the last 100 kyrs from a large suite of different archeo- and paleomagnetic field models (AFM-M, AFM-Md and AFM-H, respectively). These models allow to identify common features of the past field  and to qualitatively assess the robustness and the significance of these spatial features throughout time.

We evaluate each model over the entire period and compute structural criteria that quantify axial dipole dominance, equatorial symmetry, zonality and radial flux concentration at the CMB. These criteria are used to quantify the Earth-likeness of numerical dynamo simulations. Over 100 kyrs, the criteria show larger fluctuations than previously assumed, which implicates a wider range of numerical dynamo simulations to be considered as Earth-like.