Skip to main content

Advertisement

We’d like to understand how you use our websites in order to improve them. Register your interest.

A simple method for deriving the uniform field MT responses in auroral zones

Abstract

Source field effects in magnetotelluric data acquired at high geomagnetic latitudes can result in erroneous interpretations of Earth conductivity structure deep within the mantle. This paper describes a simple technique most appropriate for a region that is dominantly one-dimensional (1-D) and uses the vertical magnetic field variations for identifying intervals of likely low contamination by non-uniform sources. Times are chosen when the variations stay within prescribed limits defined on the basis of a histogram of the variations for the whole recording interval. An example is given showing application of the method for data from a site under the auroral oval at a time when solar activity was at its lowest for the last solar cycle. A model derived from the responses obtained by processing all available data implies a decrease in resistivity at about 350 km to about 100 Ω.m. In contrast, the model obtained from low activity interval responses shows a less rapid decrease in resistivity, without a change at around the 410 km phase boundary. The responses obtained from all data can be explained by the influence of a source with an average wavelength of 3,000 km.

References

  1. Akasofu, S.-L., Polar and Magnetospheric Substorms, 280 pp., Springer, New York, 1968.

    Google Scholar 

  2. Cagniard, L., Basic theory of the magneto-telluric method of geophysical prospecting, Geophysics, 18, 605–635, 1953.

    Article  Google Scholar 

  3. Camfield, P. A., Magnetometer array study in a tectonically active region of Quebec, Canada, Geophys. J. R. astr. Soc., 65, 553–570, 1981.

    Article  Google Scholar 

  4. Constable, S. C., R. L. Parker, and C. G. Constable, Occam’s inversion: a practical algorithm for generating smooth models from electromagnetic sounding data, Geophysics, 52, 289–300, 1987.

    Article  Google Scholar 

  5. Dmitriev, V. I. and M. N. Berdichevsky, The fundamental model of magnetotelluric sounding, Proc. IEEE, 67, 1034–1044, 1979.

    Article  Google Scholar 

  6. Egbert, G. D., Robust multiple-station magnetotelluric data processing, Geophys. J. Int., 130, 475–496, 1997.

    Article  Google Scholar 

  7. Egbert, G. D., M. Eisel, O. S. Boyd, and H. F. Morrison, DC trains and Pc3s: Source effects in mid-latitude geomagnetic transfer functions, Geophys. Res. Lett., 27, 25–28, 2000.

    Article  Google Scholar 

  8. Gamble, T. D., W. M. Goubau, and J. Clarke, Magnetotellurics with a remote reference, Geophysics, 44, 53–68, 1979.

    Article  Google Scholar 

  9. Garcia, X., A. D. Chave, and A. G. Jones, Robust processing of magnetotelluric data from the auroral zone, J. Geomag. Geoelectr., 49, 1451–1468, 1997.

    Article  Google Scholar 

  10. Hermance, J. F., Electromagnetic induction in the Earth by a moving ionospheric current system, Geophys. J. R. astr. Soc., 55, 557–576, 1978.

    Article  Google Scholar 

  11. Hermance, J. F. and W. R. Peltier, Magnetotelluric fields of a line current, J. Geophys. Res., 75, 3351–3356, 1970.

    Article  Google Scholar 

  12. Hibbs, R. D. and F. W. Jones, The calculation of the electromagnetic fields of a sheet current with arbitrary intensity distribution over a layered half space—I: The general method and results, Geophys. J. R. astr. Soc., 46, 433–452, 1976a.

    Article  Google Scholar 

  13. Hibbs, R. D. and F. W. Jones, The calculation of the electromagnetic fields of a sheet current with arbitrary intensity distribution over a layered half space—II: The computer program and its application, Geophys. J. R. astr. Soc., 46, 453–465, 1976b.

    Article  Google Scholar 

  14. Jones, A. G., Geomagnetic induction studies in Scandinavia—I. Determination of the inductive response function from the magnetometer data, J. Geophys., 48, 181–194, 1980.

    Google Scholar 

  15. Jones, A. G. and I. J. Ferguson, The electric Moho, Nature, 409, 331–333, 2001.

    Article  Google Scholar 

  16. Jones, A. G. and H. Jödicke, Magnetotelluric transfer function estimation improvement by a coherence-based rejection technique, 54th Society of Exploration Geophysics Annual General Meeting, Atlanta, Georgia, U.S.A., December 2–6, Abstract volume pages 51–55, 1984.

  17. Jones, A. G., A. D. Chave, G. Egbert, D. Auld, and K. Bahr, A comparison of techniques for magnetotelluric response function estimation, J. Geophys. Res., 94, 14,201–14,213, 1989.

    Article  Google Scholar 

  18. Kuckes, A. F., Relations between electrical conductivity of a mantle and fluctuating magnetic fields, Geophys. J. R. astr. Soc., 32, 119–131, 1973a.

    Article  Google Scholar 

  19. Kuckes, A. F., Correspondence between the magnetotelluric and field penetration depth analysis for measuring electrical conductivity, Geophys. J. R. astr. Soc., 32, 381–385, 1973b.

    Article  Google Scholar 

  20. Liu, H.-P. and D. D. Kosloff, Numerical evaluation of the Hilbert transform by the Fast Fourier Transform (FFT) technique, Geophys. J. R. astr. Soc., 67, 791–799, 1981.

    Article  Google Scholar 

  21. Mareschal, M., Source effects and the interpretation of geomagnetic sounding data at sub-auroral latitudes, Geophys. J. R. astr. Soc., 67, 125–136, 1981.

    Article  Google Scholar 

  22. Mareschal, M., Modelling of natural sources of magnetospheric origin in the interpretation of regional induction studies: a review, Surv. Geophys., 8, 261–300, 1986.

    Article  Google Scholar 

  23. Narod, B. B. and J. R. Bennest, Ring-core fluxgate magnetometers for use as observatory variometers, Phys. Earth Planet. Inter., 59, 23–28, 1990.

    Article  Google Scholar 

  24. Osipova, I. L., S. C. O. Hjelt, and L. L. Vanyan, Source field problems in northern parts of the Baltic shield, Phys. Earth Planet. Inter., 53, 337–342, 1989.

    Article  Google Scholar 

  25. Parker, R. L., The inverse problem of electromagnetic induction: existence and construction of solutions based on incomplete data, J. Geophys. Res., 85, 4421–4425, 1980.

    Article  Google Scholar 

  26. Parker, R. L. and K. A. Whaler, Numerical methods for establishing solutions to the inverse problem of electromagnetic induction, J. Geophys. Res., 86, 9574–9584, 1981.

    Article  Google Scholar 

  27. Peltier, W. R. and J. F. Hermance, Magnetotelluric fields of a Gaussian electrojet, Can. J. Earth Sci., 8, 338–346, 1971.

    Article  Google Scholar 

  28. Pettersen, F., Aurora borealis—the northern lights, Way North: Earth Science, publication from Tromsø Museum, Univ. Tromsø, 1, 1992.

  29. Pirjola, R. J., Modelling the electric and magnetic fields at the Earth’s surface due to an auroral electrojet, J. Atmos. Solar-Terrestr. Phys., 60, 1139–1148, 1998.

    Article  Google Scholar 

  30. Price, A. T., The theory of magnetotelluric fields when the source field is considered, J. Geophys. Res., 67, 1907–1918, 1962.

    Article  Google Scholar 

  31. Schmucker, U., Anomalies of geomagnetic variations in the southwestern United States, Bull. Scripps Inst. Oceanogr., Univ. Calif. Press, 13, 1970.

  32. Schmucker, U. and P. Weidelt, Electromagnetic Induction in the Earth, Lecture Notes, Aarhus Univ., Denmark, 1975.

    Google Scholar 

  33. Srivastava, S. P., Method of interpretation of magneto-telluric data when source field is considered, J. Geophys. Res., 70, 945–954, 1965.

    Article  Google Scholar 

  34. Tikhonov, A. N., On determining electric characteristics of the deep layers of the Earth’s crust, Dolk. Acad. Nauk. SSSR, 73, 295–297, 1950. Reprinted in Vozoff (1986), 2–3.

    Google Scholar 

  35. Viljanen, A., R. Pirjola, and L. Häkkinen, An attempt to reduce induction source effects at high latitudes, J. Geomag. Geoelectr., 45, 817–831, 1993.

    Article  Google Scholar 

  36. Viljanen, A., R. Pirjola, and O. Amm, Magnetotelluric source effect due to 3D ionospheric current systems using the complex image method for 1D conductivity structures, Earth Planets Space, 51, 933–945, 1999.

    Article  Google Scholar 

  37. Vozoff, K. (ed.), Magnetotelluric Methods, Soc. Expl. Geophys. Reprint Ser. No. 5, Tulsa, OK, ISBN 0-931830-36-2, 1986.

  38. Wait, J. R., On the relationship between telluric currents and the Earth’s magnetic field, Geophysics, 19, 281–289, 1954.

    Article  Google Scholar 

  39. Weidelt, P., The inverse problem of geomagnetic induction, Z. Geophys., 38, 257–289, 1972.

    Google Scholar 

  40. Weidelt, P., Entwicklung und Erdprobung eines Verfahrens zur Inversion zweidimensionaler Leitfähigkeitsstrukturen in E-Polarisation, Habilitation thesis, Dept. Math. Natural Sciences, Univ. Göttingen, 1978.

  41. Xu, Y., B. T. Poe, T. J. Shankland, and D. C. Rubie, Electrical conductivity of olivine, wadsleyite and ringwoodite under upper-mantle conditions, Science, 280, 1415–1418, 1998.

    Article  Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to Alan G. Jones.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Jones, A.G., Spratt, J. A simple method for deriving the uniform field MT responses in auroral zones. Earth Planet Sp 54, 443–450 (2002). https://doi.org/10.1186/BF03353035

Download citation

Keywords

  • Solar Cycle
  • Apparent Resistivity
  • Auroral Zone
  • Auroral Oval
  • Instantaneous Amplitude