Internal Large-Scale Toroidal Magnetic Field of the Sun

Abstract

The evolution of the large-scale toroidal magnetic field Bϕ of the Sun generating in the radiative zone by acts of differential rotation on the relict radial magnetic field Bϕ is investigated regarding the magnetic buoyancy and ohmic dissipation.

The Toroidal Magnetic Field inside the Sun

“…The expression (1) together with the helioseismological data of Duvall et al (1984), yields a maximum estimate of the toroidal field near the core of the Sun in the range 1 x 10 7 -2 x 10 8 G. Energetic constraints suggest that this toroidal field is concentrated in relatively thin magnetic flux tubes with diameters d t < 16 000 -800km, respectively (Krivodubskij, 1990). used the oscillation data of Libbrecht (1989), and found that there is a sharp radial jump of the angular velocity, Au> ~ 18nHz ~ 1.1 x 1 0 -7 rad/s at the transition from the convection zone to the radiative zone (r = 0.7 R Q ,Au/Ar ~ 1.6 x 10" 17 rad/s cm).…”

“…Recently have showed that there is a sharp radial gradient in the Sun's rotation at the base of the convection zone, near the boundary with the radiative interior. It seems to us that the sharp radial gradients of the angular velocity near the core of the Sun and at the base of the convection zone, acting on the relict poloidal magnetic field B r , must excite an intense toroidal field B^, that can compensate for the loss of the magnetic field due to magnetic buoyancy.Magnetic buoyancy plays the main role in constraining the amplitude of the magnetic induction of the toroidal field generated at the present stage of solar evolution (Dudorov et al, 1989;Krivodubskij, 1990). There, from the condition of stationarity, dB^/dt -0, neglecting ohmic dissipation, we obtained the following expression for the maximum value of the established stationary toroidal field (Dudorov et a/., 1989;Krivodubskij, 1990):…”

“…Magnetic buoyancy plays the main role in constraining the amplitude of the magnetic induction of the toroidal field generated at the present stage of solar evolution (Dudorov et al, 1989;Krivodubskij, 1990). There, from the condition of stationarity, dB^/dt -0, neglecting ohmic dissipation, we obtained the following expression for the maximum value of the established stationary toroidal field (Dudorov et a/., 1989;Krivodubskij, 1990):…”

“…Krivodubskij (1990) performed an analysis of the energetic aspects of the problem. The total magnetic energy of the excited toroidal field, E* H = EHVH (EH = -B?/87r is the magnetic energy density), cannot exceed the total kinetic energy of the rapidly rotating core, E^.…”

“…There, from the condition of stationarity, dB^/dt -0, neglecting ohmic dissipation, we obtained the following expression for the maximum value of the established stationary toroidal field (Dudorov et a/., 1989;Krivodubskij, 1990):…”