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Evidence for long-term asymmetries in the Earth's magnetic field and possible implications for dynamo theories

Merrill, R. T. and McElhinny, M. W. and Stevenson, D. J. (1979) Evidence for long-term asymmetries in the Earth's magnetic field and possible implications for dynamo theories. Physics of the Earth and Planetary Interiors, 20 (2-4). pp. 75-82. ISSN 0031-9201. https://resolver.caltech.edu/CaltechAUTHORS:20131016-151213282

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Abstract

Paleomagnetic data indicate that there is a north-south asymmetry in the time-averaged magnetic field and that there are small but significant differences between the normal and reverse polarity states. The geographical variation is most likely due to spatial variation in the boundary conditions at the core-mantle interface. The difference in the magnetic fields of the reverse and normal polarity states can be modeled in terms of a “standing field”. The paleomagnetic data are insufficient to determine whether or not this “standing field” is of core origin. However, consideration of mechanisms, including thermoelectric currents, indicates that there probably are important differences in core processes between the two polarity states. At first glance this interpretation is difficult to reconcile with the fact that the magnetic induction equation is antisymmetric with respect to the magnetic field. A way around this problem is the possibility that only certain transitions are allowed between acceptable eigenstates in dynamo models of the Earth's magnetic field.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0031-9201(79)90029-3DOIArticle
http://www.sciencedirect.com/science/article/pii/0031920179900293PublisherArticle
ORCID:
AuthorORCID
Stevenson, D. J.0000-0001-9432-7159
Additional Information:© 1979 Elsevier Scientific Publishing Company. Accepted for publication in revised form April 2, 1979. One of us (R.T.M.) is thankful for grants from the National Science Foundation and Australian National University that allowed him to carry out this research at the Australian National University; R.T.M. Would also like to thank Dr. Frank Stacey for a useful discussion on the thermoelectric model. A review of an earlier version of this manuscript by Dr. Ken Hoffman was very helpful.
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NSFUNSPECIFIED
Australian National UniversityUNSPECIFIED
Issue or Number:2-4
Record Number:CaltechAUTHORS:20131016-151213282
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131016-151213282
Official Citation:R.T. Merrill, M.W. McElhinny, D.J. Stevenson, Evidence for long-term asymmetries in the Earth's magnetic field and possible implications for dynamo theories, Physics of the Earth and Planetary Interiors, Volume 20, Issues 2–4, November 1979, Pages 75-82, ISSN 0031-9201, http://dx.doi.org/10.1016/0031-9201(79)90029-3. (http://www.sciencedirect.com/science/article/pii/0031920179900293)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41957
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:16 Oct 2013 22:20
Last Modified:03 Oct 2019 05:53

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