High-fidelity geomagnetic field intensity determination was carried out using 191 baked fragments collected from 20 kilns or hearths with ages ranging between ~1200 BC and ~AD 1725 in South Korea. Geomagnetic field intensity variation displayed three narrow minima at ~800-700 BC, ~AD 700, and ~AD 1600 and two maxima at ~1200-1100 BC and ~AD 1000-1100. In most time intervals, virtual axial dipole moment (VADM) variation is confined within 20% of the present VADM. However, geomagnetic field intensity circa 3000 yr ago is nearly 40% larger than the present value. Such high VADMs circa 3000 yr ago are in phase with those in other longitudinal bands in northern hemisphere centered at 5E (France), 30E (the Middle East) and 200E (Hawaii). Although strong geomagnetic field intensity circa 3000 yr ago is globally synchronous, the highest VADM occurs at slightly different time intervals in different locations. Hence it is possible that the globally strong geomagnetic field intensity circa 3000 yr ago reflects the migration of persistent hemispheric flux in northern hemisphere or an episode of geomagnetic field hemispheric asymmetry.
Bibliographical noteFunding Information:
Mike Jackson of the Institute for Rock Magnetism (IRM) provided tremendous help with the rock magnetic measurements. The Keck Foundation , the National Science Foundation , Earth Sciences Division , and the University of Minnesota provide funding for the IRM. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) ( NRF-2013R1A2A1A01004418 ) and by the Korea Meteorological Administration Research and Development Program under Grant CATER-2013-8070 .
- Dipolar field
- Non-dipolar field
- Secular variation
- Strong geomagnetic field intensity
ASJC Scopus subject areas
- Geochemistry and Petrology
- Space and Planetary Science
- Earth and Planetary Sciences (miscellaneous)