The shape of the geomagnetic field through the last 8,500 years over part of the northern hemisphere
Item
Title (Dublin Core)
en-US
The shape of the geomagnetic field through the last 8,500 years over part of the northern hemisphere
Description (Dublin Core)
en-US
Regional type curves depicting secular variations of declination and inclination through the last 10,000 calendar years constructed for north-western Europe (356° E, 55° N) and east-central North America (270° E, 46° N) by stacking palaeomagnetic data derived from lake sediment cores are described and analysed. The spectral content and phase relationships of the two pairs of curves show that they have a complex origin with both drifting and standing geomagnetic sources contributing to them. The strongest evidence of drifting sources is provided by the inclination type-curves which exhibit maximum correlation for a phase shift of ~650 years suggestive of westward drift at a rate of about 0.13 degrees a year. At the same time, comparison of the declination type-curves strongly suggests that waxing and waning standing sources were dominant. We show that the difference in relative importance of drifting as compared to standing geomagnetic sources implied by the patterns of correlation deduced respectively for declination and inclination can, at least in principle, be attributed to observation point/geomagnetic source geometry by modelling the secular variation that would be produced by standing but oscillating equatorial dipoles and radial dipoles located deep within the outer core, by a pair of drifting deep-seated radial dipoles of constant intensity, and by drifting sheets of radial dipoles (taken to represent current-loops) located at shallow depth within the outer core. Each of these model sources produces secular variation curves with distinctive shapes and phase relationships. Hence, an attempt is made to identify qualitatively the types and locations of the sources which dominated the secular variations as recorded by our type-curves. One of our most important conclusions is that there appears to be a' turning-point' at ~ 4 750 years before present when the relative amplitudes of the active' standing' sources changed but the characteristics of the drifting sources appear to have remained relatively unchanged.
ARK: https://n2t.net/ark:/88439/y011535
Permalink: https://geophysicsjournal.com/article/263
ARK: https://n2t.net/ark:/88439/y011535
Permalink: https://geophysicsjournal.com/article/263
Creator (Dublin Core)
Creer, K.M.
Tucholka, P.
Subject (Dublin Core)
en-US
Palaeomagnetism
en-US
Lake sediments
en-US
Secular variation
en-US
Geomagnetic field
en-US
Geodynamics
Publisher (Dublin Core)
en-US
Journal of Geophysics
Date (Dublin Core)
1982-07-29
Type (Dublin Core)
info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
en-US
Peer-reviewed Article
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
https://journal.geophysicsjournal.com/JofG/article/view/263
Source (Dublin Core)
en-US
Journal of Geophysics; Vol 51 No 1 (1982): Journal of Geophysics; 188-198
2643-2986
2643-9271
Language (Dublin Core)
eng
Relation (Dublin Core)
https://journal.geophysicsjournal.com/JofG/article/view/263/221