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The operation of the solar global dynamo appears to involve many dynamical elements. Self-consistent MHD simulations which realistically incorporate all of these processes are not yet computationally feasible, though some elements can now…

Astrophysics · Physics 2008-11-26 Allan Sacha Brun , Mark S. Miesch , Juri Toomre

The solar cycle is a complex phenomenon, a comprehensive understanding of which requires the study of various tracers. Here, we consider the solar cycle as manifested in the harmonics of the solar large-scale surface magnetic field,…

Solar and Stellar Astrophysics · Physics 2024-03-12 V. N. Obridko , A. S. Shibalova , D. D. Sokoloff

We compare the current effects of rotation in stellar evolution to those of the magnetic field created by the Tayler instability. In stellar regions, where magnetic field can be generated by the dynamo due to differential rotation (Spruit…

Astrophysics · Physics 2009-11-10 Andre Maeder , Georges Meynet

The study of the global structure of the large-scale magnetic field of the Sun is extremely important for creating a theoretical model of the dynamics of the Sun and predictions of the real situation in the helio- and geomagnetosphere. The…

Solar and Stellar Astrophysics · Physics 2023-02-13 Elena Gavryuseva

Aims. In this study, we analyse the magnetic field properties of a set of 15 global magnetohydrodynamics (MHD) simulations of solar-type star dynamos conducted using the ASH code. Our objective is to enhance our understanding of these…

Solar and Stellar Astrophysics · Physics 2024-02-14 Quentin Noraz , Allan Sacha Brun , Antoine Strugarek

The variation of the solar diameter is the subject of hot debates due to the possible effect on Earth climate and also due to different interpretations of long period solar variabilities, including the total solar irradiance. We shortly…

Solar and Stellar Astrophysics · Physics 2012-07-10 Koutchmy Serge , Bazin Cyril , Prado Jean-Yves , Lamy Philippe , Rocher Patrick

Unexplained annual variations in nuclear decay rates have been reported in recent years by a number of groups. We show that data from these experiments exhibit not only variations in time related to Earth-Sun distance, but also…

Nuclear Experiment · Physics 2011-06-09 Ephraim Fischbach , Jere H. Jenkins , Peter A. Sturrock

To explain the large-scale magnetic field of the Sun and other bodies, mean-field dynamo theory is commonly applied where one solves the averaged equations for the mean magnetic field. However, the standard approach breaks down when the…

Solar and Stellar Astrophysics · Physics 2018-06-06 A. Brandenburg , P. Chatterjee

The Sun is a variable star whose magnetic activity and total irradiance vary on a timescale of approximately 11 years. The current activity minimum has attracted considerable interest because of its unusual duration and depth. This raises…

Solar and Stellar Astrophysics · Physics 2009-07-21 A. -M. Broomhall , W. J. Chaplin , Y. Elsworth , S. T. Fletcher , R. New

Recently discovered long-term oscillations of the solar background magnetic field associated with double dynamo waves generated in inner and outer layers of the Sun indicate that the solar activity is heading in the next three decades…

Solar and Stellar Astrophysics · Physics 2020-04-13 V. V. Zharkova , S. J. Shepherd , E. Popova

The Sun is an extraordinary workbench, from which several fundamental astronomical parameters can be measured with high precision. Among these parameters, the solar radius $R_{\odot}$ plays an important role in several aspects, such as in…

Observations of the meridional circulation of the Sun, which plays a key role in the operation of the solar dynamo, indicate that its speed varies with the solar cycle, becoming faster during the solar minima and slower during the solar…

Solar and Stellar Astrophysics · Physics 2017-10-11 Gopal Hazra , Arnab Rai Choudhuri

Surface rotation rates of young solar-type stars display drastic changes at the end of the pre-main sequence through the early main sequence. This may trigger corresponding changes in the magnetic dynamos operating in these stars, which…

Solar and Stellar Astrophysics · Physics 2016-02-03 C. P. Folsom , P. Petit , J. Bouvier , J. Morin , A. Lèbre

The work is devoted to the study of periodic structures in the magnetic field of the photosphere. The polarity of the Sun's magnetic fields shows cyclicity with periods of 1-3 years, which is possibly due to quasi-biennial variations that…

Solar and Stellar Astrophysics · Physics 2025-07-08 Elena Vernova , Marta Tyasto , Dmitrii Baranov

Stability of toroidal magnetic field in a stellar radiation zone is considered for the cases of uniform and differential rotation. In the rigidly rotating radiative core shortly below the tachocline, the critical magnetic field for…

Astrophysics · Physics 2009-11-13 L. L. Kitchatinov , G. Rüdiger

Solar activity seems quite understandable when considered on the scales comparable with a solar cycle, i.e. about 11 years, and on a short time scale of about a year. A solar cycle looks basically (anti)symmetric with respect to the solar…

Solar and Stellar Astrophysics · Physics 2025-08-08 V. N. Obridko , A. S. Shibalova , D. D. Sokoloff , I. M. Livshits

The surface rotation rates of young solar-type stars vary rapidly with age from the end of the pre-main sequence through the early main sequence. Important changes in the dynamos operating in these stars may result from this evolution,…

Solar and Stellar Astrophysics · Physics 2016-01-27 C. P. Folsom , P. Petit , J. Bouvier , A. Lèbre , L. Amard , A. Palacios , J. Morin , J. -F. Donati , S. V. Jeffers , S. C. Marsden , A. A. Vidotto

The change of sound speed has been found at the base of the convection during the solar cycles, which can be used to constrain the solar internal magnetic field. We aim to check whether the magnetic field generated by the solar dynamo can…

Solar and Stellar Astrophysics · Physics 2021-06-02 Shaolan Bi , Tanda Li , Kang Liu , Jie Jiang , Yaguang Li , Jinghua Zhang , Xianfei Zhang , Yaqian Wu

During stellar evolution, especially in the PMS, stellar structure and rotation evolve significantly causing major changes in the dynamics and global flows of the star. We wish to assess the consequences of these changes on stellar dynamo,…

Solar and Stellar Astrophysics · Physics 2017-09-15 Constance Emeriau-Viard , Allan Sacha Brun

One of the puzzling features of solar magnetism is formation of long-living compact magnetic structures; such as sunspots and pores, in the highly turbulent upper layer of the solar convective zone. We use realistic radiative 3D MHD…

Solar and Stellar Astrophysics · Physics 2015-05-18 I. N. Kitiashvili , A. G. Kosovichev , A. A. Wray , N. N. Mansour