Estimating the Deep Solar Meridional Circulation Using Magnetic Observations and a Dynamo Model: A Variational Approach

Hung, Ching Pui; Jouve, L.; Brun, Allan Sacha; Fournier, Alexandre; Talagrand, O.

doi:10.1088/0004-637x/814/2/151

Cited by 13 publications

(12 citation statements)

References 51 publications

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“…with C 0 = 2.3 × 10 3 kg m −3 . Expressions 32 and 33 result in a meridional velocity field very similar in shape to those obtained in numerical simulations [18], and also similar to the simplest circulation pattern of those used in kinematic dynamo models [39,40,11]. The magnitude of the latitudinal velocity near the surface is about 12 m s −1 .…”

Section: Numerical Simulationsupporting

confidence: 67%

Large-scale Model of the Axisymmetric Dynamo with Feedback Effects

Sraibman

Minotti

2019

Sol Phys

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A dynamo model is presented, based on a previously introduced kinematic model, in which the reaction of the magnetic field on the mass flow through the Lorentz force is included. Given the base mass flow corresponding to the case with no magnetic field, and assuming that the modification of this flow due to the Lorentz force can be treated as a perturbation, a complete model of the large-scale magnetic field dynamics can be obtained. The input needed consists in the large-scale meridional and zonal flows, the small-scale magnetic diffusivity, and a constant parameter entering the expression of the α-effect. When applied to a solar-like star, the model shows a realistic dynamics of the magnetic field, including cycle duration, consistent field amplitudes with the correct parity, progression of the zonal magnetic field towards the equator, and motion toward the poles of the radial field at high latitudes. Also, the radial and zonal components show a correct phase relation, and, at the surface level, the magnetic helicity is predominantly negative in the northern hemisphere and positive in the southern hemisphere.

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Section: Numerical Simulationsupporting

confidence: 67%

Large-scale Model of the Axisymmetric Dynamo with Feedback Effects

Sraibman

Minotti

2019

Sol Phys

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“…It seems safe to say that at present, hybrid mean-field models incorporating all evident sources of poloidal field give the best agreement with observations (see, e.g., Dikpati et al 2004). In light of the central role that meridional flows play in many of these models (e.g., Jouve and Brun 2007b;Guerrero and de Gouveia Dal Pino 2008;Brun and Rempel 2009;Nandy et al 2011;Hazra et al 2014), measurements of that flow are particularly crucial, and are an area of great current interest (see, e.g., Hathaway 2012; Zhao et al 2013;Schad et al 2013;Dikpati et al 2014;Hung et al 2015;Sun et al 2015) and discussion in ). We will return briefly to these measurements in Sect.…”

Section: Open Issues and Overviewmentioning

confidence: 98%

Magnetism, dynamo action and the solar-stellar connection

Brun

Browning

2017

Living Rev Sol Phys

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252

182

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The Sun and other stars are magnetic: magnetism pervades their interiors and affects their evolution in a variety of ways. In the Sun, both the fields themselves and their influence on other phenomena can be uncovered in exquisite detail, but these observations sample only a moment in a single star's life. By turning to observations of other stars, and to theory and simulation, we may infer other aspects of the magnetism-e.g., its dependence on stellar age, mass, or rotation rate-that would be invisible from close study of the Sun alone. Here, we review observations and theory of magnetism in the Sun and other stars, with a partial focus on the "Solar-stellar connection": i.e., ways in which studies of other stars have influenced our understanding of the Sun and vice versa. We briefly review techniques by which magnetic fields can be measured (or their presence otherwise inferred) in stars, and then highlight some key observational findings uncovered by such measurements, focusing (in many cases) on those that offer particularly direct constraints on theories of how the fields are built and maintained. We turn then to a discussion of how the fields arise in different objects: first, we summarize some essential elements of convection and dynamo theory, including a very brief discussion of mean-field theory and related concepts. Next we turn to simulations of convection and magnetism in stellar interiors, highlighting both some peculiarities of field generation in different types of stars and some unifying physical processes that likely influence dynamo action in general. We conclude with a brief

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“…Under the assumption that meridional flow modulations are the main factor controlling the buildup of the poloidal field from AR sources, Hung et al (2015), Hung et al (2017) suggest an inverse approach to derive flow variations from magnetic data. As, however, we will see in the next subsection, the validity of the underlying assumption is open to question.…”

Section: Photospheric Flow Variationsmentioning

confidence: 99%

Solar cycle prediction

Petrovay

2020

Living Rev Sol Phys

200

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A review of solar cycle prediction methods and their performance is given, including early forecasts for Cycle 25. The review focuses on those aspects of the solar cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming solar maximum no later than right after the start of the given cycle. Prediction methods form three main groups. Precursor methods rely on the value of some measure of solar activity or magnetism at a specified time to predict the amplitude of the following solar maximum. The choice of a good precursor often implies considerable physical insight: indeed, it has become increasingly clear that the transition from purely empirical precursors to model-based methods is continuous. Model-based approaches can be further divided into two groups: predictions based on surface flux transport models and on consistent dynamo models. The implicit assumption of precursor methods is that each numbered solar cycle is a consistent unit in itself, while solar activity seems to consist of a series of much less tightly intercorrelated individual cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variations are the same at any point of time, and therefore it lends itself to analysis and forecasting by time series methods. In their overall performance during the course of the last few solar cycles, precursor methods have clearly been superior to extrapolation methods. One method that has This article is a revised version of

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Estimating the Deep Solar Meridional Circulation Using Magnetic Observations and a Dynamo Model: A Variational Approach

Cited by 13 publications

References 51 publications

Large-scale Model of the Axisymmetric Dynamo with Feedback Effects

Large-scale Model of the Axisymmetric Dynamo with Feedback Effects

Magnetism, dynamo action and the solar-stellar connection

Solar cycle prediction

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