קולוקוויום בחוג לגאופיזיקה: Rapid Changes in the Geomagnetic Field: Signs of Collapse or Natural Evolution?

Zoom: https://tau-ac-il.zoom.us/j/89059154709?pwd=u4Gphpi2sUOcLmQNlI9jPzVwblPdiX.1

Abstract:

Earth’s magnetic field is constantly changing over timescales ranging from a few years to millions of years. One of the primary goals of paleomagnetic research is to characterize how and when these variations have occurred. After decades of study, we now know that the field has existed for at least the past four billion years, that it has maintained a predominantly dipolar structure for most of geological time, and that it has reversed its polarity at least several hundred times. However, our understanding of the field’s recent history - over the past several millennia - remains limited due to inherent uncertainties in the global paleomagnetic database.

In this presentation, I will review our project aimed at reconstructing the behavior of the geomagnetic field over the past 10,000 years with unprecedented temporal resolution - on the order of decades or better. To achieve this, we developed methods to accurately reconstruct the geomagnetic field intensity from well-dated archaeological materials. By analyzing hundreds of such samples, collected from various archaeological sites in Israel, we produced a high-resolution curve of geomagnetic field intensity over the past several millennia. The resulting curve reveals extreme short-term features in the field that were previously unrecognized, including the highest field intensity and the fastest rate of change ever documented. I will discuss the geomagnetic implications of these findings, their relevance for understanding the geodynamo, and their potential to predict the future geomagnetic behavior—including whether the current field decay may be a precursor to a polarity reversal to a collapse of the field. Finally, I will demonstrate how our new full-vector (intensity and direction) secular variation curve can also be used to date archaeological materials and geological sequences such as lake sediments. 

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מארגן האירוע: ד"ר אריאל ללוש