Astronomical School’s Report, 2019, Volume 15, Issue 2, Pages 25–32
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UDC 523.98

Generation of the toroidal magnetic field in the radiant zone of the Sun and alternation of the amplitude of the neighboring magnetic cycles

Krivodubskij V.N.

Astronomical Observatory of Taras Shevchenko National University of Kyiv, Observatorna str. 3, 04053 Kyiv, Ukraine


The processes of restructuring of the deep toroidal magnetic field, which is excited by radial differential rotation in a stable radiant zone filled with the primary (relic) poloidal magnetic field, are analyzed. According to the data of helioseismological experiments on the internal rotation of the Sun, the radial angular velocity gradient covers layers of the ray zone deeper than the solar convective zone (SCZ). We believe that this radial angular velocity gradient acts on the primary diploid type poloidal field and thus excites a toroidal field (Ω-effect) of a time-constant direction, which will be pushed out of the generation zone due to magnetic buoyancy. From the steady state condition, when the Ω-effect compensates for the field losses caused by magnetic buoyancy, we derived a formula for estimating the maximum value of a stationary toroidal field, which can be maintained in the radiating zone for a long time. Taking into account the intensity of the relict radial field in the radiant zone Br≈ 0,1...10 G, the radial angular velocity gradient (∂Ω/∂r ≈ 7⋅10-18 rad/s⋅cm) determined from helioseismological measurements is capable of generating a sufficiently strong deep toroidal magnetic field BT≈106...108 G. Toroidal fields, the magnitude of which outweighs these steady-state values, are gradually removed from the radiant zone due to magnetic buoyancy into the higher layers of the SCZ where the αΩ-dynamo mechanism operates. In view of this, the total toroidal field in the SCZ will consist of two components: variable and stationary. The first magnetic component is excited by the dynamo process and so it changes its direction (polarity) with a period of 11 years. At the same time, the second component of permanent orientation, which penetrates into the SCZ from below (from the radiant zone), cannot be the cause of cyclicity. However, it will be affect the amplitude of neighboring cycles of solar activity. In one cycle, the total toroidal field, when the directions of the two components of the field coincide, will have a greater intensity than in the neighboring cycle, when the directions of these components are opposite. Since the intensity of the sunspots formation is determined by the floating up to the solar surface of the total toroidal field, this should ultimately lead to the observed alternation of the amplitude of the neighboring 11-year cycles of solar activity.

Keywords: Sun; radiant zone; relic magnetic field; helioseismological experiments; inner rotation of the Sun; magnetic buoyancy; convective zone; turbulent dynamo; 11-year cycle of solar activity


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