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Application of A. C. demagnetization to investigate the stability of rock magnetization caused by lightning currents

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Summary

An apparatus is described which enables progressive demagnetization of rock specimens under alternating fields in order to remove the unstable components of magnetization while retaining a measurable fraction of the stable component.

The apparatus is utilized to study the stability of magnetization created in rock specimens by artificial lightning currents. It is shown that the remanent magnetization due to strong lightning currents could be fairly stable and in certain cases peak a. c. fields of intensity as high as 1700 Oe may fail to destroy completely the effect of this hard component.

Possible means for avoiding the ‘magnetic noise’ effect of lightning on paleomagnetic investigations are discussed.

Zusammenfassung

Es wird eine Apparatur beschrieben die es ermöglicht, Gesteinsproben mit Hilfe von Wechselfeldern schrittweise zu Entmagnetisieren. Dabei werden die unstabilen Komponenten der Magnetisierung entfernt, während ein Teil der stabilen Magnetisierung erhalten bleibt.

Die Apparatur wurde verwendet, um die Stabilität der in den Gesteinsproben durch künstliche Beblitzung erzeugten Magnetisierung zu untersuchen. Es wird gezeigt, dass die durch starke Blitze erzeugte remanente Magnetisierung recht stabil sein kann und dass es in gewissen Fällen selbst Wechselfeldern mit Feldstärken bis zu 1700 Oe nicht gelingt, diese harte Magnetisierung zum Verschwinden zu bringen.

Möglichkeiten, um den störenden Einfluss der Blitze bei päleomagnetischen Untersuchungen zu vermeiden, werden besprochen.

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Authors and Affiliations

  1. Department of Geophysics, Swiss Federal Institute of Technology, Zurich, Switzerland

    P. Vallabh Sharma

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  1. P. Vallabh Sharma
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Additional information

Part II of the dissertation ‘Theoretical study of the magnetic attraction due to rock bodies and experimental investigation of the stability of rock magnetism’ submitted to the Swiss Federal Institute of Technology (ETH), Zurch, for the degree of Doctor of Natural Sciences.

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Vallabh Sharma, P. Application of A. C. demagnetization to investigate the stability of rock magnetization caused by lightning currents. PAGEOPH 64, 110–120 (1966). https://doi.org/10.1007/BF00875536

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  • DOI: https://doi.org/10.1007/BF00875536

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