In this work, we present 16 directional and 27 intensity high‐quality values from Iberia. Moreover, we have updated the Iberian archeomagnetic catalogue published more than 10 years ago with a considerable increase in the database. This has led to a notable improvement of both temporal and spatial data distribution. A full vector paleosecular variation curve from 1000 BC to 1900 AD has been developed using high‐quality data within a radius of 900 km from Madrid. A hierarchical bootstrap method has been followed for the computation of the curves. The most remarkable feature of the new curves is a notable intensity maximum of about 80 μT around 600 BC, which has not been previously reported for the Iberian Peninsula. We have also analyzed the evolution of the paleofield in Europe for the last three thousand years and conclude that the high maximum intensity values observed around 600 BC in the Iberian Peninsula could respond to the same feature as the Levantine Iron Age Anomaly, after travelling westward through Europe.
1 March 2021 in Earth and Planetary Science Letters
Since the publication of the European archaeomagnetic field model SCHA.DIF.3k in 2009, the number of paleomagnetic data derived from archaeological materials such as baked clays and volcanic rocks coming from Europe has increased by about 90% for directions and around 180% for intensities. Taking advantage of this increase, here we provide an updated regional archaeomagnetic model, called SCHA.DIF.4k, for the European continent and adjacent areas and now covering the last four millennia. To model the three geomagnetic elements, declination, inclination, and intensity, we use the regional R‐SCHA2D technique in space and temporal basis of cubic splines. A critical selection of the archaeomagnetic and volcanic data available in a spherical cap of 30° centered at 40°N latitude and 10°E longitude has been considered. In addition, in order to better constrain the behavior of the archaeomagnetic field during the last centuries, we include the historical data of the HISTMAG compilation. The new regional model allows us to better define the paleomagnetic field over Europe as well as to generate new paleosecular variation curves for archaeomagnetic dating purposes. Using these curves, the dating precision has been estimated for the last 4 kyr. As expected, results show that it strongly depends on the data uncertainties, the temporal data distribution and the behavior of the geomagnetic field itself. In addition, the use of the full vector geomagnetic field, instead of the directional information exclusively, provides more precise archaeomagnetic dating results.
1 October 2020 in Physics of the Earth and Planetary Interiors
Significance: The geodynamo, the process that produces and controls the evolution of the Earth’s magnetic field, is still not fully understood. Despite the success of current numerical geodynamo models in reproducing some geomagnetic observations, their high complexity and computational requirements hinder their use for certain studies. Here, we present a simple model based on random fluctuations that is able to reproduce the temporal asymmetry of the dipolar strength of the field observed during polarity reversals. This behavior arises due to the existence of two parts of the model that are energetically unbalanced, imposing a preferred direction of energy transfer, and we propose that the same mechanism would be the cause of the temporal asymmetry of the geodynamo.