Article | Open | Published:
Revision of the high-degree Gauss coefficients in the IGRF 1945–1955 models by using natural orthogonal component analysis
Earth, Planets and Spacevolume 54, pages753–761 (2002)
The high-degree Gauss coefficients (n ≥ 7) in the IGRF models for 1945–1955 exhibit some unusual and unreliable behaviors in comparison with the models for other epochs. In this paper the method of Natural Orthogonal Components (NOC) is used to revise these coefficients. The obtained result shows that the main geomagnetic field can be approximated very well by the first a few NOC eigen modes. The high-degree Gauss coefficients (n ≥ 7) are deduced for each of IGRF models using the first 6 eigen modes and low-degree Gauss coefficients (n ≤ 6). The deduced high-degree coefficients are in very good agreement with the original ones for all models except those for 1945, 1950 and 1955. In comparison with the unusual behaviors in the IGRF1945–1955 models, the deduced high-degree coefficients for these models exhibit fairly smooth time-variations. Besides, the magnetic energy and magnetic flux calculated by the revised Gauss coefficients show more continuous secular variations and consistent characteristics.
Barton, C. E., International geomagnetic field: the seventh generation, J. Geomag. Geoelectr., 49, 123, 1997.
Frynberg, E. B., Separation of the geomagnetic field into a normal and anomalous part, Geomagn. Aeron., 15, 117, 1975.
Golovkov, V. P., N. E. Papitashvili, Y. S. Tyupkin, and E. P. Kharin, Separation of geomagnetic field variations on the quiet and disturbed components by the MNOC, Geomagn. Aeron., 18, 511, 1978.
Golovkov, V. P., T. N. Bondar, and I. A. Burdelnaya, Spatial-temporal modeling of the Geomagnetic field for 1980–2000 period and a candidate IGRF secular-variation model for 2000–2005, Earth Planets Space, 52, 1125, 2000.
IAGA Commission 2 Working Group 4, International Geomagnetic ReferenceField 1965.0, J. Geophys. Res., 74, 4407, 1969.
IAGA Division 5, Working Group 8, International Geomagnetic Reference Field 2000, Geophys. J. Int., 141, 259, 2000.
Kendall, M. G. and A. Stuart, The Advanced Theory of Statistics, vol. 3, chap. 35, Charles Griffin, London, 1976.
Langel, R. A., The Main Field, in Geomagnetism, Vol. 1, edited by J. A. Jacobs, pp. 249–512, Academic Press, London, 1987.
Langel, R. A. and R. H. Estes, Derivation of proposed International Geomagnetic Reference Field models for 1945, 1950, 1955, and 1960, Phys. Earth Planet. Int., 48, 293, 1987.
Langel, R. A., D. R. Barraclough, D. J. Kerridge, V. P. Golovkov, T. J. Sabaka, and R. H. Estes, Definitive IGRF models for 1945, 1950, 1955, and 1960, J. Geomag. Geoelectr., 40, 645, 1988.
Leove, M., Probability Theory, second edition, D Van Nosthand Company Inc., New York, 1963.
Lowes, F. J., An estimate of the errors of the IGRF/DGRF fields 1945–2000, Earth Planets Space, 52, 1207, 2000.
Pushkov, A. N., E. B. Frynberg, T. A. Chernova, and M. V. Fiskina, Analysis of the space-time structure of the main geomagnetic field by expansion into natural orthogonal components, Geomagn. Aeron., 16, 196, 1976.
Rotanova, N. M., N. E. Papitashvili, and A. N. Pushkov, Use of natural orthogonal components to distinguish and analyze the 60-yr geomagnetic field variations, Geomagn. Aeron., 22, 821, 1982.
Sabaka, T. J., R. A. Langel, R. T. Baldwin, and J. A. Conrad, The geomagnetic field 1900–1995, including the large-scale field from magnetospheric sources, and the NASA candidate models for the 1995 revision of the IGRF, J. Geomag. Geoelectr., 49, 157, 1997.
Sun, W., W.-Y. Xu, and S.-I. Akasofu, Mathematical separation of directly driven and unloading components in the ionospheric equivalent currents during substorms, J. Geophys. Res., 103, 11695, 1998.
Sun, W., W.-Y. Xu, and S.-I. Akasofu, An improved method to deduce the unloading component for magnetospheric substorms, J. Geophys. Res., 105, 13131, 2000.
Xu, W.-Y., Unusual behaviour of the IGRF during the 1945–1955 period, Earth Planets Space, 52, 1227, 2000.
Yamada, Y., 2-day, 3-day, and 5-6-day oscillations of the geomagnetic field detected by principal component analysis, Earth Planets Space, 54, 379, 2002.
Zmuda, A. J., The International Geomagnetic Reference Field, 1965.0, in IAGA Bulletin 28, World Magnetic Survey, IUGG, Paris, 1971.