Collaborative Research: Levantine geomagnetic field spike: How high, how fast, how far?

在过去的七千年里，采矿活动在欧洲和亚洲的许多地方留下了大量的材料。因为铜冶炼需要在熔炉中高温熔化矿石，所以有大量的木炭与铜渣密切相关，从而能够直接测定考古残骸的年代。事实证明，冶金碎屑可以很好地保留古代地磁强度的记录。这一点，再加上前所未有的测年能力，意味着我们现在可以获得场强变化的高分辨率记录。我们已经记录了约旦(公元前10世纪)的一段时间，那里的磁场强度非常高，几乎是现在磁场的三倍。这种地磁场“尖峰”一定发生得非常快。将这些数据与希腊附近研究的数据进行比较，表明希腊的主曲线与约旦的数据之间存在显著差异。为了评估造成这种差异的各种可能原因(例如，地磁场中的极短波长特征、遗漏的地磁场中的极高频时间变化等)，我们正在挖掘第二个遗址，该遗址靠近包含“尖峰”的遗址，并与“尖峰”遗址和塞浦路斯的一个具有类似材料的遗址同时代。考古学和古代地磁场(古地磁学)的结合本质上是跨学科的，在这两个学科中都有广泛的影响。跨学科研究在实践中是困难的，因为研究生需要成为各自领域的专家，并冒着以牺牲深度为代价变得过于宽泛的风险。在我们的研究中，我们通过让两个研究生紧密合作来处理这个问题，每个研究生都坚定地植根于一个学科，但从另一个学生那里学到了很多关于另一个学科的知识。这种跨学科努力的好处是广泛的。从研究地球磁场的角度来看，全球范围内强度变化的准确图像(该项目对此作出贡献但不能自行解决的目标)对于诸如“地面真实”数值模型和理解放射性碳生产的变化以及放射性碳时间刻度的校准等不同的努力至关重要。从考古学的角度来看，将考古材料放在一个紧密的时间框架内一直是一个挑战，我们的工作已经被用于解决考古金相学中的测年难题。

Mining activity has left enormous piles of material in numerous places around Europe and Asia spanning the last seven millennia. Because copper smelting requires melting of ore at high temperatures in furnaces, there is abundant charcoal intimately associated with the copper slag, enabling the direct dating of the archaeological debris. It turns out that metallurgical debris can retain an excellent record of the ancient geomagnetic field strength. This, combined with unprecedented ability to date the material, means that high resolution records of changes in field strength are now available to us. We have already documented a period of time in Jordan (10th century BCE) of extraordinarily high magnetic field strengths, nearly three times the present field. This geomagnetic field "spike" must have happened very quickly. Comparison of these data with those from nearby studies in Greece suggest that there is a significant discrepancy between the Grecian master curve and the data from Jordan. To assess the various possible causes for this discrepancy (e.g., extremely short wavelength features in the geomagnetic field, extremely high frequency temporal changes in the geomagnetic field missed, etc.), we are excavating a second site near to and co-eval with the site containing the "spike" and a co-eval site in Cyprus that has comparable material. The combination of archaeology and the study of the ancient geomagnetic field (paleomagnetism) is inherently interdisciplinary, with broad impacts in both disciplines. Interdisciplinary research is difficult in practice because graduate students need to become expert in their own fields and run the risk of becoming too broad at the expense of depth. We are handling this problem in our research by having two graduate students work closely together, each firmly rooted in one discipline but learning a great deal about the other discipline from the other student. The benefits of such interdisciplinary efforts are wide ranging. From the point of view of studying the geomagnetic field, an accurate picture of intensity changes on a global scale (a goal to which this project contributes but does not solve by itself) is essential for such different endeavors as "ground truthing" numerical models and understanding variations in the production of radiocarbon and the calibration of the radiocarbon time scale. From the archaeological perspective, placing archaeological materials in a tight temporal framework is always a challenge and our work is already being put to use to solve dating puzzles in archaeometallurgy.