Abstract
The solar magnetic field on a surface of 2.5 solar radii, known as the source surface, can be approximated by a dipole field. This dipolar field rotates by 180° meridionally throughout a sunspot cycle, although the polar unipolar fields on the photosphere do not show such a shift across the equator. It is of interest to assume that the solar source surface corresponds to the surface of the magnetized planets and that the photosphere corresponds to the core surface. An advantage of the solar situation is that one can directly observe the photospheric magnetic fields which correspond to the magnetic fields of the core surface. We examine why the dipolar field on the source surface is inclined with respect to the rotation axis and why the inclination angle changes from 0° to 180° (or 180° to 0°) during a sunspot cycle. We assume that the main dipole is axially aligned with the rotation axis, because the unipolar fields in the polar regions do not shift across the equator. It can be shown that the inclination and its change arise from the growth and decay of a few dipolar sources oriented in an east-west direction near the equator. The combined field of the axially aligned dipole and the equatorial dipoles provides an inclined dipole on the source surface. The equatorial dipoles are identified as large-scale weak dipolar fields which contain active regions. The rotation of the dipole on the source surface arises from a relative change of strength of the equatorial dipoles and the axial dipole. On the basis of the above study of the solar situation, we suggest that the inclination and eccentricity of the dipole axis of the magnetized planets (including the earth) arise from the growth and decay of equatorial dipoles near the core surface. The reversal of the earth’s dipole field may be explained in a way similar to the reversal of the dipole field on the source surface.
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References
Allan, D.W. (1958) Reversals of the earth’s magnetic field. Nature 181, 469.
Bullard, E.C. and H. Gellman (1954) Homogeneous dynamos and terrestrial magnetism. Phil. Trans. Roy. Soc. A. 247, 213.
Busse, F.H. (1978) Magnetohydrodynamics of the earth’s dynamo. Ann. Rev. Fluid Mech. 10, 435.
Chapman, S. and J. Bartels (1940) Geomagnetism, II, Oxford Univ. Press, Oxford.
Cox, A. (1970) Geomagnetic reversals. Science 163, 237.
Dodson, R.F., I.R. Dunn, M.D. Fuller, I. Williams, H. Ito, V.A. Schmidt and Y.-M. Wu (1978) Paleomagnetic record of a late Tertiary field reversal. Geophys. J.R. Astr. Soc. 53, 373.
Elsasser, W.M. (1946) Induction effects in terrestrial magnetism. Phys. Rev. 69, 106 and 70, 202.
Fuller, M.D., I. Williams and K.A. Hoffman (1979) Paleomagnetic records of geomagnetic field reversals and the morphology of the transitional fields. Rev. Geophys. Space Phys. 17, 179.
Gubbins, D. (1984) The earth’s magnetic field. Contemp. Phys. 25, 269.
Hoeksema, J.T. and P.H. Scherrer (1984) Harmonic analysis of the solar magnetic field, Proceedings of the 4th European Meeting on Solar Physics, The Hydromagnetics of the Sun, Eur. Space Agency Spec. Publ., ESA-SP-220, 269.
Hoeksema, J.T., J.M. Wilcox and P.H. Scherrer (1982) Structure of the heliospheric current sheet in the early portion of sunspot cycle 21. J. Geophys. Res. 87, 10331.
Hoeksema, J.T., J.M. Wilcox and P.H. Scherrer (1983) The structure of the heliospheric current sheet. J. Geophys. Res. 88, 9910.
Levine, R.H. (1977) Large scale solar magnetic fields and coronal notes. In Coronal Holes and High Speed Wind Stream, edited by J.B. Zirker, p. 103, Colorado Associated University Press, Boulder, Colo.
Levy, E.H. (1972) Kinematic reversal schemes for the geomagnetic dipole. Astrophys. J. 171, 635.
McFadden, P.C. and R.T. Merrill (1984) Lower mantle convection and geomagnetism. J. Geophys. Res. 89, 3354.
Merrill, R.T. and M.W. McElhinny (1983) The Earth’s Magnetic Field, Academic Press.
Moffatt, H.K. (1978) Magnetic Field Generation in Electrically Conducting Fluids, Cambridge Univ. Press, Cambridge.
Ness, N.F., M.H. Acuña, K.W. Behannon, L.F. Burlaga, J.E.P. Connerney, R.P. Lepping and F.M. Neubauer (1986) Magnetic fields at Uranus. Science 233, 85.
Ness, N.F., M.H. Acuña, L.F. Burlaga, J.E.P. Connerney, R.P. Lepping and F.M. Neubauer (1989) Magnetic fields at Neptune. Science 246, 1473.
Prevot, M., E.A. Mankinen, R.S. Coe and C.S. Grommé (1985) The Steens Mountain (Oregon) polarity transition 2, Field intensity variations and discussion of reversal models. J. Geophys. Res. 90, 10417.
Rikitake, T. (1958) Oscillations of a system of disc dynamos. Proc. Camb. Phil. Soc. 54, 89.
Rikitake, T. (1966) Electromagnetism and the Earth’s Interior, Elsevier, Amsterdam.
Roberts, N. and J. Shaw (1984) The relationship between the magnitude and direction of the I geomagnetic field during the Late Tertiary in Eastern Iceland. Geophys. J. R. Astr. Soc. 76. 637.
Roberts, N. and J.D.A. Piper (1989) A description of the behavior of the earth’s magnetic field. In Geomagnetism, 3, ed. by J.A. Jacobs, p. 163, Academic Press Ltd., London.
Saito, T. and S .-I. Akasofu (1987) On the reversal of the dipolar field of the Sun and its possible implication for the reversal of the Earth’s field. J. Geophys. Res. 92, 1255.
Saito, T., T. Oki, C. Olmsted and S.-I. Akasofu (1989) A representation of the magnetic neutral line on the solar source surface in terms of the sun’s axial dipole at the center and two equatorial dipoles in the photosphere. J. Geophys. Res. 94, 14993.
Saito, T., Y. Kozuka, T. Oki and S.-I. Akasofu (1991) The source surface and photospheric magnetic field models. J. Geophys. Res. 90, 3807.
Shatten, K.H., J.M. Wilcox and N.F. Ness (1969) A model of coronal and interplanetary magnetic fields. Sol. Phys. 9, 422.
Wang, Y.-M., A.G. Nash and N.R. Sheeley, Jr. (1989) Magneticflux transport on the sun. Science 245, 712.
Williams, LS. and M. Fuller (1981) Zonal harmonic models of reversal transition field. J. Geophys. Res. 86, 11657.
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© 1993 Springer Science+Business Media Dordrecht
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Akasofu, SI., Saito, T. (1993). Reversals of the Solar Source Surface Magnetic Field and of the Planets. In: Stone, D.B., Runcorn, S.K. (eds) Flow and Creep in the Solar System: Observations, Modeling and Theory. NATO ASI Series, vol 391. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-8206-3_3
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DOI: https://doi.org/10.1007/978-94-015-8206-3_3
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