Assessment of extreme archeomagnetic intensity variations during the era of geomagnetic spikes using a transdimensional Bayesian inversion

Archeomagnetic datasets describing geomagnetic field intensity variation over time are not only often sparse, but have errors in both age and measurement, making model-fitting a challenge. Modelling often assumes a prescribed temporal discretisation which, when coupled with sparse data coverage, requires strong damping in order to ensure smoothness and restricts interpretation of rapid changes. Transdimensional Bayesian inversion is a powerful alternative method that produces the posterior probability distribution of intensity change over time, whose temporal complexity is not set a priori but is self-selected by the data. Here we show the application of this technique to the construction of a new curve of the intensity evolution over the period 2000 BC - 0 AD for the Near East. We will assess the evidence for extreme variations, termed geomagnetic spikes, that have been previously inferred for the period ca. 1000-700 BC.