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Semi-annual variation of the geomagnetic field

Abstract

Nighttime hourly mean values of D, H and Z (or X, Y and Z in a few cases) from 113 observatories for the interval 1964.0 to 1966.0 have been analyzed to determine the semi-annual variation. Results from the 84 observatories with dip latitudes between ±60° have been subjected to spherical harmonic analysis to determine the coefficients of the internal and external parts. Only those coefficients that are found to be significantly different from zero at the 5 per cent level have been included.

One of the main objectives is to obtain a reliable estimate, with confidence limits, of the internal/external ratio at a very low frequency for constraining estimates of the deep conductivity of the mantle. It is shown that a model that includes only the principal P 01 term can lead to a seriously misleading internal/external ratio.

References

  • Akaike, H., A new look at the statistical model identification, IEEE Trans. Autom. Contr., AC-19, 716–723, 1974.

    Article  Google Scholar 

  • Anderssen, R. S., On the solutions of certain overdetermined systems of linear equations that arise in geophysics, J. Geophys. Res., 74, 1045–1051, 1969.

    Article  Google Scholar 

  • Banks, R. J., The overall conductivity distribution of the earth, J. Geomag. Geoelectr., 24, 337–351, 1972.

    Article  Google Scholar 

  • Black, D. I., Lunar and solar magnetic variations at Abinger: their detection and estimation by spectral analysis via Fourier transformation, Phil. Trans. R. Soc. London, A268, 233–263, 1970.

    Article  Google Scholar 

  • Butcher, E. C. and D. M. Schlapp, The annual variation of the night-time values of the geomagnetic field, Geophys. J. Int., 111, 151–158, 1992.

    Article  Google Scholar 

  • Campbell, W. H., Secular, annual, and semi-annual changes in the baseline level of the Earth’s magnetic field at North American locations, J. Geophys. Res., 85, 6557–6571, 1980.

    Article  Google Scholar 

  • Campbell, W. H., Annual and semiannual variations of the geomagnetic field at equatorial locations, J. Atmos. Terr. Phys., 43, 607–616, 1981.

    Article  Google Scholar 

  • Fukushima, N. and T. Nagata, Morphology of magnetic disturbance, Ann. Geophys., 24, 1–11, 1968.

    Google Scholar 

  • Gupta, J. C. and S. Chapman, Some statistics concerning the daily geomagnetic character figure Cp, Pure Appl. Geophys., 68, 103–113, 1967

    Article  Google Scholar 

  • Harwood, J. M. and S. R. C. Malin, Sunspot cycle influence on the geomagnetic field, Geophys. J. R. Astr. Soc., 50, 605–619, 1977.

    Article  Google Scholar 

  • Hibberd, F. M., The geomagnetic Sq variation—annual, semiannual and solar cycle variations and ring current effects, J. Atmos. Terr. Phys., 47, 341–352, 1985.

    Article  Google Scholar 

  • Malin, S. R. C., Worldwide distribution of geomagnetic tides, Phil. Trans. R. Soc. London, A274, 551–594, 1973.

    Article  Google Scholar 

  • Malin, S. R. C. and A. M. Işkara, Annual variation of the geomagnetic field, Geophys. J. R. Astr. Soc., 47, 445–457, 1976.

    Article  Google Scholar 

  • Malin, S. R. C. and D. M. Schlapp, Geomagnetic lunar analysis by least squares, Geophys. J. R. Astr. Soc., 60, 409–418, 1980.

    Article  Google Scholar 

  • Malin, S. R. C. and D. E. Winch, Annual variation of the geomagnetic field, Geophys. J. Int., 124, 170–174, 1996.

    Article  Google Scholar 

  • Malin, S. R. C., M. K. Tunçer, and O. Yazici-Çakim, Systematic analysis of magnetic observatory data—1. A proposed method, Geophys. J. Int., 126, 635–644, 1996.

    Article  Google Scholar 

  • McCreadie, H. and E. C. Butcher, Preliminary analysis of annual and semiannual variations of the geomagnetic field, Explor. Geophys., 24, 151–156, 1993.

    Article  Google Scholar 

  • McIntosh, D. H., On the annual variation of magnetic disturbance, Phil. Trans. R. Soc. London, A251, 525–552, 1959.

    Article  Google Scholar 

  • McLeod, M. G., Magnetospheric and ionospheric signals in magnetic observatory monthly means: electrical conductivity of the deep mantle, J. Geophys. Res., 99, 13577–13590, 1994.

    Article  Google Scholar 

  • Rangarajan, G. K. and B. N. Bhargava, Long term changes in the amplitude and phase of the semiannual and annual variations in low latgitude geomagnetic field, J. Geomag. Geoelectr., 39, 437–446, 1987.

    Article  Google Scholar 

  • Rastogi, R. G., Geomagnetic field variations at low latitudes and ionospheric electric fields, J. Atmos. Terr. Phys., 55, 1375–1381, 1993.

    Article  Google Scholar 

  • Rastogi, R. G., S. Alex, and A. Patil, Seasonal variations of geomagnetic D, H and Z fields at low latitudes, J. Geomag. Geoelectr., 46, 115–126, 1994.

    Article  Google Scholar 

  • Russell, C. T. and R. L. McPherron, Semi-annual variation of geomagnetic activity, J. Geophys. Res., 78, 92–108, 1973.

    Article  Google Scholar 

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Malin, S.R.C., Winch, D.E. & Işıkara, A.M. Semi-annual variation of the geomagnetic field. Earth Planet Sp 51, 321–328 (1999). https://doi.org/10.1186/BF03352236

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  • DOI: https://doi.org/10.1186/BF03352236

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