Analysis of geomagnetic field intensity variations in Mesopotamia during the third millennium BC with archeological implications

Gallet, Yves; Fortin, Michel; Fournier, Alexandre; Goff, Maxime Le; Livermore, Philip W.

doi:10.1016/j.epsl.2020.116183

Cited by 20 publications

(34 citation statements)

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“…The chain length is 10 8 . These parameters are close to the parameters defined by Gallet et al (2020); for more details on the AH-RJMCMC code and algorithm, see Livermore et al (2018). of fragment groups Hazor XVI-A and Hazor XVII-F.…”

Section: Bayesian Modelingsupporting

confidence: 58%

“…For an in-depth review on the method and the selection criteria, see Le Goff and Gallet (2004), Genevey et al (2009), and Hartmann et al (2010). Table 2 lists the selection criteria of the Triaxe method (see also Gallet et al, 2020).…”

Section: Tablementioning

confidence: 99%

“…The archeointensity data from Turkey, Syria, Jordan, Cyprus, and Israel, published over the past decades (Ben‐Yosef et al., 2017; Ben‐Yosef et al., 2008, 2009; Ertepinar et al., 2012, 2016, 2020; Gallet et al., 2006, 2008, 2014a, 2015, 2020; Gallet & Al‐Maqdissi, 2010; Gallet & Butterlin, 2015; Gallet & Le Goff, 2006; Genevey et al., 2003; Shaar et al., 2011, 2015, 2016; Stillinger et al., 2015) potentially provide sufficient information to inspect the behavior of the field in this region with an improved resolution and accuracy. Yet, when these recent data are plotted together with all other data published since the 1980s, substantial discrepancies arise (Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Synchronizing Geomagnetic Field Intensity Records in the Levant Between the 23rd and 15th Centuries BCE: Chronological and Methodological Implications

Shaar

Bechar

Finkelstein

et al. 2020

Geochem Geophys Geosyst

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Section: Bayesian Modelingsupporting

confidence: 58%

Section: Tablementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synchronizing Geomagnetic Field Intensity Records in the Levant Between the 23rd and 15th Centuries BCE: Chronological and Methodological Implications

Shaar

Bechar

Finkelstein

et al. 2020

Geochem Geophys Geosyst

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“…Considering a total duration of 100 yr, a variation rate of 0.1 μT yr -1 , and the commonly accepted value of 0.6 m 2 s −1 for the magnetic diffusivity, such features would be reachable for a flow speed greater than 40 km yr -1 , more than twice its current rms value (∼15 km yr -1 ). For the third millennium BC, Gallet et al (2020) also report two Figure 11. Instantaneous rate of change of the intensity of the field generated by flux expulsion as a function of the characteristic velocity of the fluid in the Earth's core and the characteristic scale of the process in the core, given for different initial intensity and magnetic diffusivity.…”

Section: Discussionmentioning

confidence: 99%

Imprint of magnetic flux expulsion at the core–mantle boundary on geomagnetic field intensity variations

Troyano

Fournier

Gallet

et al. 2020

Geophysical Journal International

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SUMMARY During the last decade, rapid or extreme geomagnetic field intensity variations associated with rates greater than the maximum currently observed have been inferred from archeomagnetic data in the Near-East and in Western Europe. The most extreme events, termed geomagnetic spikes, are defined as intensity peaks occurring over a short time (a few decades), and are characterized by high variation rates, up to several μT yr–1. Magnetic flux expulsion from the Earth’s outer core has been suggested as one possible explanation for these peaks but has not yet been examined in detail. In this study, we develop a 2-D kinematic model for magnetic flux expulsion whose key control parameter is the magnetic Reynolds number Rm, the ratio of magnetic diffusion time to advection time. This model enables the tracking of magnetic field lines which are distorted and folded by a fixed flow pattern. Two processes govern the magnetic evolution of the system. The first is the expulsion of magnetic flux from closed streamlines, whereby flux gradually concentrates near the boundaries of the domain, which leads to an increase of the magnetic energy of the system. If the upper boundary separates the conducting fluid from an insulating medium, a second process then takes place, that of diffusion through this interface, which we can quantify by monitoring the evolution of the vertical component of magnetic induction along this boundary. It is the conjunction of these two processes that defines our model of magnetic flux expulsion through the core–mantle boundary. We analyse several configurations with varying flow patterns and magnetic boundary conditions. We first focus on flux expulsion from a single eddy. Since this specific configuration has been widely studied, we use it to benchmark our implementation against analytic solutions and previously published numerical results. We next turn our attention to a configuration which involves two counter-rotating eddies producing an upwelling at the centre of the domain, and comprises an upper boundary with an insulating medium. We find that the characteristic rise time and maximum instantaneous variation rate of the vertical component of the magnetic field that escapes the domain scale like $\sim R_m^{0.15}$ and $\sim R_m^{0.45}$, respectively. Extrapolation of these scaling laws to the Earth’s régime is compared with various purported archeointensity highs reported in the Near-East and in Western Europe. According to our numerical experiments magnetic flux expulsion is unlikely to produce geomagnetic spikes, while intensity peaks of longer duration (one century and more) and smaller variation rates appear to be compatible with this process.

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“…For the reconstruction of EMF variations over the last decades and centuries, direct measurements from geomagnetic observatories and satellites are now available. Prior to the instrumental data, geomagnetic field variations can only be recovered from the study of well-dated volcanic rocks, archaeological artefacts and sediments (Gallet et al 2020). Altogether, instrumental measurements and palaeomagnetic data, compiled in online databases such as Magnetic Information Consortium (MagIC, http://www.earthref.org) or GEOMAGIA50 (https://geomagia.gfz-potsdam.de), are the fundamental starting points for computing geomagnetic field models at regional and global levels (e.g.…”

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confidence: 99%

Geomagnetic field variations in the past: an introduction

Chiara

Herrero‐Bervera²,

Tema

2020

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In the last decades, palaeomagnetic research has provided us with a picture of the temporal and spatial behaviour of the Earth's magnetic field (EMF) from its origin up to the present day. Well-dated palaeomagnetic data offer important sources of information about the past variation of the geomagnetic field and have shown that it is characterized by temporal fluctuations such as reversals, excursions and spikes. Despite the advances in our understanding of EMF behaviour, the current dataset is biased towards high and northern latitudes and, therefore, several questions remain open to debate, such as the origin and evolution of the EMF and the frequency and spatial distribution of its variations. This Special Publication focuses on the study of the temporal and spatial evolution of the EMF in the past through new data from palaeomagnetic and rock magnetic studies of archaeological materials, sediments and lavas from Europe, Africa, Australia, New Zealand, India and Baltic Sea, and their applications in archaeology, stratigraphy and climate. This paper summarizes our current knowledge on geomagnetic field variations in the past, open questions and future challenges and gives an overview of the volume's context, which aims to disclose fundamental properties of the Earth's magnetic field evolution. EMF variation in the past: state of the art and open questions Reference data and mathematical models have shown that the EMF is characterized by continuous spatial

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Analysis of geomagnetic field intensity variations in Mesopotamia during the third millennium BC with archeological implications

Abstract: This is a repository copy of Analysis of geomagnetic field intensity variations in Mesopotamia during the third millennium BC with archeological implications.

Cited by 20 publications

References 34 publications

Synchronizing Geomagnetic Field Intensity Records in the Levant Between the 23rd and 15th Centuries BCE: Chronological and Methodological Implications

Synchronizing Geomagnetic Field Intensity Records in the Levant Between the 23rd and 15th Centuries BCE: Chronological and Methodological Implications

Imprint of magnetic flux expulsion at the core–mantle boundary on geomagnetic field intensity variations

Geomagnetic field variations in the past: an introduction

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