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The sunspot number varies roughly periodically with time. However the individual cycle durations and the amplitudes are found to vary in an irregular manner. It is observed that the stronger cycles are having shorter rise times and vice…

Solar and Stellar Astrophysics · Physics 2012-05-04 Bidya Binay Karak

We present in this work the development of a solar data assimilation method based on an axisymmetric mean field dynamo model and magnetic surface data, our mid-term goal is to predict the solar quasi cyclic activity. Here we focus on the…

Solar and Stellar Astrophysics · Physics 2017-11-15 Ching Pui Hung , Allan Sacha Brun , Alexandre Fournier , Laurène Jouve , Olivier Talagrand , Mustapha Zakari

One obvious feature of the solar cycle is its variation from one cycle to another. In this article, we review the dynamo models for the long-term variations of the solar cycle. By long-term variations, we mean the cycle modulations beyond…

Solar and Stellar Astrophysics · Physics 2023-07-05 Bidya Binay Karak

Solar cycles vary in their amplitude and shape. There are several empirical relations between various parameters linking cycle's shape and amplitude, in particular the Waldmeier relations. As solar cycle is believed to be a result of the…

Solar and Stellar Astrophysics · Physics 2012-05-24 V. V. Pipin , D. D. Sokoloff , I. G. Usoskin

Inter-cycle variations in the series of 11-year solar activity cycles have a significant impact on both the space environment and climate. Whether solar cycle variability is dominated by deterministic chaos or stochastic perturbations…

Solar and Stellar Astrophysics · Physics 2025-05-12 Zi-Fan Wang , Jie Jiang , Jing-Xiu Wang

Context. Solar activity cycles vary in amplitude and duration. The variations can be at least partly explained by fluctuations in dynamo parameters. Aims. We want to restrict uncertainty in fluctuating dynamo parameters and find out which…

Solar and Stellar Astrophysics · Physics 2018-07-18 L. L. Kitchatinov , A. V. Mordvinov , A. A. Nepomnyashchikh

The 11-year sunspot cycle has many irregularities, the most promi- nent amongst them being the grand minima when sunspots may not be seen for several cycles. After summarizing the relevant observational data about the irregularities, we…

Solar and Stellar Astrophysics · Physics 2015-06-18 Arnab Rai Choudhuri

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

Solar cycles are studied with the Version 2 monthly smoothed international sunspot number, the variations of which are found to be well represented by the modified logistic differential equation with four parameters: maximum cumulative…

Solar and Stellar Astrophysics · Physics 2018-12-19 G. Qin , S. -S. Wu

Using the non-linear mean-field dynamo models we calculate the magnetic cycle parameters, like the dynamo cycle period, the amplitude of the total magnetic energy, and the Poynting flux luminosity from the surface for the solar analogs with…

Solar and Stellar Astrophysics · Physics 2021-01-27 V. V. Pipin

We show how magnetic observations of the Sun can be used in conjunction with an axisymmetric flux-transport solar dynamo model in order to estimate the large-scale meridional circulation throughout the convection zone. Our innovative…

Solar and Stellar Astrophysics · Physics 2017-10-06 Ching Pui Hung , Laurène Jouve , Allan Sacha Brun , Alexandre Fournier , Olivier Talagrand

The Sun, aside from its eleven year sunspot cycle is additionally subject to long term variation in its activity. In this work we analyse a solar-like convective dynamo simulation, containing approximately 60 magnetic cycles, exhibiting…

Solar and Stellar Astrophysics · Physics 2017-10-11 Frederick A. Gent , Maarit J. Käpylä , Jörn Warnecke

Direct observations over the past four centuries show that the number of sunspots observed on the Sun's surface vary periodically, going through successive maxima and minima. Following sunspot cycle 23, the Sun went into a prolonged minimum…

Solar and Stellar Astrophysics · Physics 2013-03-05 Dibyendu Nandy , Andrés Muñoz-Jaramillo , Petrus C. H. Martens

This article reviews some of the leading results obtained in solar dynamo physics by using temporal oscillator models as a tool to interpret observational data and dynamo model predictions. We discuss how solar observational data such as…

Solar and Stellar Astrophysics · Physics 2014-07-21 Ilídio Lopes , Dário Passos , Melinda Nagy , Kristof Petrovay

Physics-based solar cycle predictions provide an effective way to verify our understanding of the solar cycle. Before the start of cycle 25, several physics-based solar cycle predictions were developed. These predictions use flux transport…

Solar and Stellar Astrophysics · Physics 2023-02-08 Jie Jiang , Zebin Zhang , Kristóf Petrovay

The solar activity cycle is successfully modeled by the flux transport dynamo, in which the meridional circulation of the Sun plays an important role. Most of the kinematic dynamo simulations assume a one-cell structure of the meridional…

Solar and Stellar Astrophysics · Physics 2014-02-05 Gopal Hazra , Bidya Binay Karak , Arnab Rai Choudhuri

The magnetic field of the Sun is generated by internal dynamo process with a cyclic period of 11 years or a 22 year magnetic cycle. The signatures of the Sun's magnetic cycle are observed in the different layers of its atmosphere and in its…

Solar and Stellar Astrophysics · Physics 2023-09-26 Sandra V. Jeffers , Rene Kiefer , Travis S. Metcalfe

The predictability, or lack thereof, of the solar cycle is governed by numerous separate physical processes that act in unison in the interior of the Sun. Magnetic flux transport and the finite time delay it introduces, specifically in the…

Astrophysics · Physics 2009-11-13 A. R. Yeates , D. Nandy , D. H. Mackay

The sunspot number data during the past 400 years indicates that both the profile and the amplitude of the solar cycle have large variations. Some precursors of the solar cycle were identified aiming to predict the solar cycle. The polar…

Solar and Stellar Astrophysics · Physics 2015-06-15 Jie Jiang

The Sun's polar magnetic fields are directly related to solar cycle variability. The strength of the polar fields at the start (minimum) of a cycle determine the subsequent amplitude of that cycle. In addition, the polar field reversals at…

Solar and Stellar Astrophysics · Physics 2014-08-01 Lisa Upton , David H. Hathaway