Double maxima 11-year solar cycles

1Krivodubskij, VN
1Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2017, 33(1):55-80
https://doi.org/10.15407/kfnt2017.01.055
Start Page: Solar Physics
Language: Russian
Abstract: 

We propose a scenario to explain the observed phenomenon of double maxima of sunspot cycles, including the generation of the magnetic field near the bottom of the solar convection zone (SCZ) and its subsequent removal from the deep layers to the surface in the “royal zone”. Five processes are involved for reconstructing of the magnetic field: the Ω-effect, magnetic buoyancy, macroscopic turbulent diamagnetism, rotary ∇ρ-effect and meridional circulation. It was found that the reconstruction of magnetism in the high-latitude and equatorial domains of the SCZ occurs in different modes. A key role in the developed mechanism of double maxima play two waves of toroidal fields from the lower base of the SCZ bottom to the solar surface in the equatorial domain. Deep toroidal fields are excited due to the Ω-effect near tachocline at the beginning of the cycle. Then these fields are transported to the surface due to combined acting of magnetic buoyancy, macroscopic turbulent diamagnetism and rotary magnetic ∇ρ-flow in the equatorial domain. Over time these magnetic fragments can be seen as bipolar sunspot groups in the middle latitudes in the “royal zone”. This first wave of toroidal fields, which is directed up, gives the main maximum of sunspot activity. However, the underlying toroidal fields in the high-latitude polar domains at the beginning of the cycle are blocked near bottom of the SCZ by two antibuoyancy effects, directed downward turbulent diamagnetic transfer and magnetic ∇ρ-pumping. Deep meridional flow toward the equator transfers these fields to the low latitudes of the equatorial domain (where there are favourable conditions for magnetic floating) during about 1-2 years. Then “belated” magnetic fields float up /rise up to surface (second wave of toroidal field). This second portion of toroidal fields, coming to the solar surface at low latitudes, leads to second (repeated) sunspot maximum.

Keywords: 11-year solar cycles, magnetic fields, maximum of sunspot activity, toroidal fields

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