Advertisement

pure and applied geophysics

, Volume 125, Issue 1, pp 67–90 | Cite as

The secular variation of the geomagnetic field in Egypt in the last 5000 years

  • A. Gouda Hussain
Article

Abstract

The palaeo-intensities (Fa) of the geomagnetic field in Egypt at some ages are determined by archaeomagnetic measurements and found to be:Fa=36.2 μT at 3100 B.C., Fa=46.8 μT at 3000 B.C.,Fa=36.5 μT at 2780 B.C., 49.0 μT at 2500 B.C., 36.4 μT at 2200 B.C., 57.5 μT at 1990 B.C., 62.1 μT atca 1400 B.C., 61.5 μT at 1400 B.C., 69.9 μT at 600 B.C., 59.3 μT at 550 B.C., 79.9 μT at 460 B.C., 73.7 μT at 450 B.C., 69.7 μT at 320 B.C., 56.2 μT at A.D. 50, 64.9 μT, at A.D. 400, 54.4 μT at A.D. 300, 57.5 μT at A.D. 700 and 43.0 μT at A.D. 1975.

The palaeo-inclinations (Ia) at some ages are found to be:Ia=24.2° at 420 B.C., 44° at A.D. 50, 60.7° at A.D. 703 and 42° at A.D. 1795.

The measured values ofFa are affected by the anisotropy of magnetic susceptibility of the samples by 13% to 20% of the expected correct value. The suitable correction of this effect is by multiplyingF by 1/((1+0.2(θ/90)) andF by 1/((1–0.13 (θ/90)), whereF andF are the resultant values ofFa if the laboratory field is perpendicular or parallel to the wall of the sample during the Thelliers' experiments, respectively, and θ is the angle between the direction of natural remnant magnetization of the sample and the direction of the laboratory field.

The results of this paper, together with the previous results for Egypt and the neighbourhoods, lead to the production of the secular variation curve of the geomagnetic field in Egypt for the last 5000 years. The intensity of the field shows a periodicity of about 400 years with multiples.

Key words

Secular variation geomagnetic field Egypt 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Aitken, M. J., Allsop, A. L., Bussel, G. D. and Winter, M. B. (1984),Geomagnetic intensity in Egypt and Western Asia during the second millennium B.C. Nature310, 205–206.Google Scholar
  2. Athavale, R. M. (1969),Intensity of the geomagnetic field in prehistoric Egypt. Earth Planet. Sci. Lett.6, 221–224.Google Scholar
  3. Bucha, V. (1967),Intensity of the Earth's magnetic field during archaeological times in Czechoslovakia. Archaeom.10, 12–25.Google Scholar
  4. Fahim, M. andHussain, A. G. (1977),The secular variation of the geomagnetic field at Helwan, Egypt. Helw. Instit. Astr. Geophys. Bull.139, 1–19.Google Scholar
  5. Fox J. M. W. andAitken M. J. (1980),Cooling-rate dependence of thermoremnent magnetization. Nature283, 462–463.Google Scholar
  6. Hussain, A. G. (1983),Archaeomagnetic investigations in Egypt: Inclination and field intensity determinations. J. Geophys.53, 131–140.Google Scholar
  7. Rogers, J., Fox, J. M. W. andAitken, M. J. (1979),Magnetic anisotropy in ancient pottery. Nature277, p. 644.Google Scholar
  8. Thellier, E. andThellier, C. (1959),Sur l'intenite du champ magnetique terrestre dans le passe historique et géologique. Ann. Geophys.,15, 185–376.Google Scholar
  9. Walton, D. (1982),Errors and resolution of thermal technique for obtaining the geomagnetic intensity, Nature295, 512–515.Google Scholar
  10. Wienert, K. A. (1970),Notes on geomagnetic observatory and survey practice, Unesco, printed in Belgium.Google Scholar

Copyright information

© Birkhäuser Verlag 1987

Authors and Affiliations

  • A. Gouda Hussain
    • 1
  1. 1.Faculty of Earth SciencesKing Abdulaziz UniversityJeddahSaudi Arabia

Personalised recommendations