The Geomagnetic Field During the Holocene

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The Geomagnetic Field during the Holocene The Holocene covers the past 10 kyr, a period in which there has been tremendous growth in human knowledge and technology. Throughout this time records of the changing geomagnetic field have been preserved in archeological artifacts, recently erupted lava flows, and rapidly deposited sediments distributed around the world. Compilations of archeomagnetic and paleomagnetic records, whose dates can often be identified to high accuracy, are being used to make continuous time-varying geomagnetic field models that extend back to 10~ka. These regularized models, known as CALS10K, represent the spatial and temporal variations of the field with spherical harmonics and cubic B-splines respectively. Work under this proposal is improving existing models by updating data compilations, and developing new inversion techniques to incorporate records of relative geomagnetic paleointensity variations derived from sediments. Models with the highest possible temporal resolution are under development in order to study fine scale variations in geomagnetic dipole moment.The resulting CALS10K models are going to be used to address a series of outstanding geomagnetic questions:How dominant is the dipole over the longer term? How long has the S. Atlantic magnetic anomaly existed? How has it evolved with time? Is the magnetic field and its secular variation persistently lower in the Pacific than in the Atlantic hemisphere?Is there observational evidence for wave motion in the geomagnetic field? On what time scales? What might be its physical origin?Data sets, tools, and products that are being developed will be archived in the MagIC community database.