Magnetic Coupling of the Solar Hemispheres During the Solar Cycle
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Magnetic Coupling of the Solar Hemispheres During the Solar Cycle V.N. Obridko1 · V.G. Fainshtein2 · Y.S. Zagainova1 · G.V. Rudenko2
Received: 15 May 2020 / Accepted: 30 September 2020 © Springer Nature B.V. 2020
Abstract This work is devoted to the study of peculiarities in the magnetic coupling of the solar hemispheres over a solar activity cycle. Two approaches have been used. We have studied (i) the magnetic coupling of active regions (ARs) located in different hemispheres in the vicinity of the central meridian and, simultaneously, in the vicinity of the equator and (ii) the properties and time variation of the meridional component of the equatorial magnetic field derived from a potential-field source surface (PFSS) reconstruction at the heliocentric distance of 1.1 solar radii. In the first case, it was shown that most of the ARs in the selected pairs were magnetically connected by field lines in their leading parts. In the second case, the magnetic field monthly mean meridional component, Bθ , in the equatorial plane, which magnetically connects the two hemispheres, displayed a cyclic time variation. In the process, the extreme values of Bθ (both positive and negative) coincided in time with the sunspot maxima, and the amplitude of the Bθ extreme values decreased with decreasing height of the sunspot activity cycle. The sign of the Bθ extreme value was opposite to the sign of the forthcoming extreme value of the polar field, while the sign of Bθ coincided with that of the field lines connecting the leading spots. This means that the polar field is indeed generated by the trailing spots of ARs, and the magnetic flux of the leading spots closes through the equator. Keywords Solar cycle · Magnetic field · Dynamo
B V.N. Obridko
[email protected] V.G. Fainshtein [email protected] Y.S. Zagainova [email protected] G.V. Rudenko [email protected]
1
Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Troitsk, Moscow, 142190, Russia
2
Institute of Solar-Terrestrial Physics of the Siberian Branch of the RAS, Irkutsk, Russia
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V.N. Obridko et al.
1. Introduction The solar cycle is a fundamental characteristic of time variations in the solar atmosphere and its phenomena. These variations are closely related to the process of magnetic field generation in the convection zone. Using MHD, Parker (1955) described the generation scheme of the solar magnetic field, including the transformation of the poloidal field located in the meridional plane into the toroidal field component perpendicular to the poloidal one due to the differential rotation ( effect) and, vice versa, the transformation of the toroidal field component into the poloidal one (α effect). Several mechanisms for the α dynamo have been proposed (Charbonneau, 2010). The toroidal field component is concentrated in the low-latitude region in the vicinity of the equator. The magnetic flux tubes that are formed in the process are ejected by buoyancy to the surfa
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