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Space current around the earth obtained with Ampère’s law applied to the MAGSAT orbit and data


An application of Ampère’s law to the MAGSAT orbit and data enabled us to study the net space current (total intensity I) flowing through the plane enclosed by the satellite orbit, and its dependence on the ground magnetic disturbance revealed in the Kp- or AE-index. Even on magnetically quiet days, MAGSAT often (or sometimes persistently) detected minor or moderate disturbances in the polar regions, in particular inside the auroral oval, without increasing Kp- or AE-values. Such disturbances are attributable to field-aligned currents into or out of the ionosphere, which produce a magnetic field (of toroidal nature) detectable above the ionosphere associated with a weak magnetic field on the ground, resulting in an occasional poor correlation of I with Kp- or AE-indices. The calculated I-values on quiet days are shown to be the order of 105 A, with a small-range UT variation. During magnetic storms or substorms the I-values become one order of magnitude greater, and the net space current is always antisunward, with its intensity roughly proportional to the AE-index values. The antisunward space current under the MAGSAT level is the Pedersen current in the ionosphere, and it constitutes the return current of the westward partial ring current (flowing at a distance of several earth radii in the dusk-side magnetosphere) along with the field-aligned currents between the partial ring current and the high-latitude ionosphere in the dayside and nightside hemispheres. The antisunward ionospheric current under the MAGSAT level contributes to a noticeable enhancement in the dawn-dusk asymmetry of the H-decrease at MAGSAT level in comparison with the ground data at the developing stage of magnetic storms or substorms.


  1. Barfield, J. N., N. A. Saflekos, R. E. Sheehan, R. L. Carovillano, T. A. Potemra, and D. Knecht, Three-dimensional observations of Birkeland currents, J. Geophys. Res., 91, 4393–4403, 1986.

  2. Bythrow, P. F. and T. A. Potemra, The relationship of total Birkeland currents to the merging electric field, Geophys. Res. Lett., 10, 573–576, 1983.

  3. Crooker, N. U. and R. L. McPherron, On the distinction between the auroral electrojet and partial ring current systems, J. Geophys. Res., 77, 6886–6889, 1972.

  4. Crooker, N. U. and G. L. Siscoe, A study of the geomagnetic disturbance field asymmetry, Radio Sci., 6, 495–501, 1971.

  5. Crooker, N. U. and G. L. Siscoe, Birkeland currents as the cause of the low-latitude asymmetric disturbance field, J. Geophys. Res., 86, 11,201–11,210, 1981.

  6. Cummings, W. D., Asymmetric ring currents and the low-latitude distur-bance daily variation, J. Geophys. Res., 71, 4495–4503, 1966.

  7. Engebretson, M. J., L. J. Cahill, Jr., T. A. Potemra, L. J. Zanetti, R. L. Arnoldy, S. B. Mende, and T. J. Rosenberg, On the relationship between morning sector irregular magnetic pulsations and field aligned currents, J. Geophys. Res., 89, 1602–1612, 1984.

  8. Fujii, R. and T. Iijima, Control of the ionospheric conductivities on large-scale Birkeland current intensities under geomagnetic quiet condi-tions, J. Geophys. Res., 92, 4505–4513, 1987.

  9. Fukushima, N., Generalized theorem for no ground magnetic effect of vertical currents connected with Pedersen currents in the uniform-conductivity ionosphere, Rep. Ionos. Space Res. Japan, 30, 35–40, 1976.

  10. Fukushima, N. and Y. Kamide, Partial ring current models for worldwide geomagnetic disturbances, Rev. Geophys. Space Phys., 11, 795–853, 1973.

  11. Hughes, T. J., D. D. Wallis, J. R. Burrows, and M. D. Wilson, Model predictions of magnetic perturbations observed by MAGSAT in dawn-dusk orbit, Geophys. Res. Lett., 9, 357–360, 1982.

  12. Iijima, T. and T. A. Potemra, Large-scale characteristics of field-aligned currents associated with substorms, J. Geophys. Res., 83, 599–615, 1978.

  13. Iijima, T. and T. Shibaji, Global characteristics of northward IMF-associated (NBZ) field-aligned currents, J. Geophys. Res., 92, 2408–2424, 1987.

  14. Iijima, T., N. Fukushima, and R. Fujii, Transverse and parallel geomag-netic perturbations over the polar regions observed by MAGSAT, Geophys. Res. Lett., 9, 369–372, 1982.

  15. Iijima, T., T. A. Potemra, L. J. Zanetti, and P. F. Bythrow, Large-scale Birkeland currents in the dayside polar region during strongly north-ward IMF: A new Birkeland current system, J. Geophys. Res., 89, 7441–7452, 1984.

  16. Iyemori, T., Storm-time magnetospheric currents inferred from mid-latitude geomagnetic field variations, J. Geomag. Geoelectr., 42, 1249–1265, 1990.

  17. Iyemori, T. and D. R. K. Rao, Decay of the Dst field of geomagnetic disturbance after substorm onset and its implication to storm-substorm relation, Ann. Geophys., 14, 608–618, 1996.

  18. Iyemori, T., T. Ikeda, and A. Nakagawa, Amplitude distribution of small-scale magnetic fluctuations over the polar ionosphere observed by Magsat, J. Geophys. Res., 90, 12,335–12,339, 1985.

  19. Kamide, Y. and N. Fukushima, Positive geomagnetic bays in evening high-latitudes and their possible connection with partial ring current, Rept. Ionos. Space Res. Japan, 26, 79–101, 1972.

  20. Kamide, Y., D. S. Evans, and J. C. Cain, A comparison of field-aligned current signatures simultaneously observed by the MAGSAT and TIROS/NOAA spacecraft, J. Geomag. Geoelectr., 36, 521–527, 1984.

  21. Kan, J. R., T. Iijima, and S.-I. Akasofu, A model of coupled radial and azimuthal current loops associated with substorms, J. Geophys. Res., 95, 21,291–21,295, 1990.

  22. Klumpar, D. M. and D. M. Greer, A technique for modeling the magnetic perturbations produced by field-aligned current systems, Geophys. Res. Lett., 9, 361–364, 1982.

  23. Lanchester, B. S. and D. D. Wallis, Magnetic field disturbances over auroral arcs observed from Spitsbergen, J. Geophys. Res., 90, 2473–2480, 1985.

  24. Langel, R. A., The magnetic earth as seen from MAGSAT, initial results, Geophys. Res. Lett., 9, 239–242, 1982.

  25. Langel, R. A., G. Ousley, J. Berbert, J. Murphy, and M. Settle, The MAGSAT mission, Geophys. Res. Lett., 9, 243–245, 1982.

  26. Maeda, H., T. Iyemori, T. Araki, and T. Kamei, New evidence of a meridional current system in the equatorial ionosphere, Geophys. Res. Lett., 9, 337–340, 1982.

  27. Maeda, H., T. Kamei, T. Iyemori, and T. Araki, Geomagnetic perturba-tions at low latitudes observed by Magsat, J. Geophys. Res., 90, 2481–2486, 1985.

  28. Potemra, T. A., L. J. Zanetti, P. F. Bythrow, A. T. Y. Lui, and T. Iijima, By-dependent convection patterns during northward interplanetary magnetic field, J. Geophys. Res., 89, 9753–9760, 1984.

  29. Suzuki, A. and N. Fukushima, Sunward or anti-sunward electric current in space below the MAGSAT level, Geophys. Res. Lett., 9, 345–347, 1982.

  30. Suzuki, A. and N. Fukushima, Anti-sunward space current below the MAGSAT level during magnetic storms, J. Geomag. Geoelectr., 36, 493–506, 1984.

  31. Suzuki, A., M. Yanagisawa, and N. Fukushima, Antisunward space current below the Magsat level during magnetic storms and its possible connection with partial ring current in the magnetosphere, J. Geophys. Res., 90(B3), 2465–2471, 1985.

  32. Wallis, D. D., J. R. Burrows, T. J. Hughes, and M. D. Wilson, Eccentric dipole coordinates for MAGSAT data presentation and analysis of external current effects, Geophys. Res. Lett., 9, 353–356, 1982.

  33. Yamada, Y., M. Takeda, and T. Araki, Field-aligned currents during northward interplanetary magnetic field, Memoirs Kakioka Mag. Obs., 23, 39–51, 1990 (in Japanese with English abstract).

  34. Yamauchi, M. and T. Araki, The interplanetary magnetic field By-de-pendent field-aligned current in the dayside polar cap under quiet conditions, J. Geophys. Res., 94, 2684–2690, 1989.

  35. Yanagisawa, M., Derivation of crustal magnetic anomalies from MAGSAT, The Inst. Space and Astronautical Sci. Rep. No. 609, 1–65, 1984.

  36. Zanetti, L. J. and T. A. Potemra, Correlated Birkeland current signatures from the TRIAD and MAGSAT magnetic field data, Geophys. Res. Lett., 9, 349–352, 1982.

  37. Zanetti, L. J., T. A. Potemra, and M. Sugiura, Evaluation of high latitude disturbances with MAGSAT (The importance of the MAGSAT geo-magnetic field model), Geophys. Res. Lett., 9, 365–368, 1982.

  38. Zanetti, L. J., W. Baumjohann, and T. A. Potemra, Ionospheric and Birkeland current distributions inferred from the MAGSAT magne-tometer data, J. Geophys. Res., 88, 4875–4884, 1983.

  39. Zanetti, L. J., T. A. Potemra, T. Iijima, W. Baumjohann, and P. F. Bythrow, Ionospheric and Birkeland current distributions for north-ward interplanetary magnetic field: inferred polar convection, J. Geophys. Res., 89, 7453–7458, 1984.

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Correspondence to Akira Suzuki.

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Suzuki, A., Fukushima, N. Space current around the earth obtained with Ampère’s law applied to the MAGSAT orbit and data. Earth Planet Sp 50, 43–56 (1998).

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  • Interplanetary Magnetic Field
  • Magnetic Storm
  • Geomagnetic Disturbance
  • Auroral Zone
  • Auroral Oval