The Nonlinear Breakup of the Sun’s Toroidal Field

  • D. W. Hughes
  • F. Cattaneo
Part of the Astrophysics and Space Science Library book series (ASSL, volume 156)


There are good reasons for believing that the sun has a strong toroidal magnetic field in the stably-stratified region of convective overshoot sandwiched between the radiative zone and convective zone proper. We have modelled the magnetic field in this region by studying the behaviour of a layer of uniform field embedded in a sub-adiabatic atmosphere. Since the field can support extra mass, such a configuration is top-heavy and instabilities of the Rayleigh-Taylor type can occur. By numerical integration of the 2-dimensional compressible MHD equations we have followed the evolution of this instability into the nonlinear regime. The initial buoyancy-driven instability of the magnetic field gives rise to strong shearing motions, thereby exciting secondary Kelvin-Helmholtz instabilities which wrap the gas into regions of intense vorticity. The somewhat surprising subsequent motions are determined primarily by the strong interactions between vortices.


Convection Zone Magnetic Layer Toroidal Field Random Initial Condition Magnetic Buoyancy 
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  1. CATTANEO, F. & HUGHES, D.W. 1988 The nonlinear breakup of a magnetic layer: instability to interchange modes. J. Fluid Mech. 196, 323–344.ADSCrossRefGoogle Scholar
  2. DALY, B.J. 1967 Numerical study of two fluid Rayleigh-Taylor instability. Phys. Fluids 10, 297–307.ADSzbMATHCrossRefGoogle Scholar
  3. HUGHES, D.W. & CATTANEO, F. 1987 A new look at the instability of a stratified horizontal magnetic field. Geophys. Astrophys. Fluid Dyn. 39, 65–81.ADSzbMATHCrossRefGoogle Scholar
  4. MOFFATT, H.K. 1983 Transport effects associated with turbulence with particular attention to the influence of helicity. Rep. Prog. Phys. 46, 621–664.ADSCrossRefGoogle Scholar
  5. PARKER, E.N. 1975 The generation of magnetic fields in astrophysical bodies. X. Magnetic buoyancy and the solar dynamo. Astrophys. J. 198, 205–209.ADSCrossRefGoogle Scholar
  6. SPIEGEL, E.A. 1987 Hydrostatic adjustment time for the solar subconvective layer. In The Internal Solar Angular Velocity, eds. B.R. Durney and S. Sofia (D.Reidel), 321–327.Google Scholar
  7. SPIEGEL, E.A. & WEISS, N.O. 1980 Magnetic activity and variations in solar luminosity. Nature 287, 616–617.ADSCrossRefGoogle Scholar
  8. VAN BALLEGOOIJEN, A.A. 1982 The overshoot layer at the base of the solar convective zone and the problem of magnetic flux storage. Astron. Astrophys. 113, 99–112.ADSzbMATHGoogle Scholar

Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • D. W. Hughes
    • 1
  • F. Cattaneo
    • 2
  1. 1.D.A.M.T.PUniversity of CambridgeCambridgeUK
  2. 2.J.I.L.AUniverisity of ColoradoBoulderUSA

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