Large-scale Model of the Axisymmetric Dynamo with Feedback Effects

Sraibman, Laura; Minotti, F.

doi:10.1007/s11207-018-1350-1

Cited by 5 publications

(8 citation statements)

References 48 publications

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“…Eridani are well-determined from accurate observations. The stellar surface differential rotation derived in Croll et al (2006) and the internal structure obtained from seismic analysis in Gai et al (2008), both from MOST photometry, allow us to obtain precise parameters for our dynamo model, based on the model developed in Sraibman & Minotti (2019) for the Sun.…”

Section: Resultsmentioning

confidence: 99%

“…In the present work we adopt the model developed in Sraibman & Minotti (2019), where magnetic feedback on the mass flow was included.…”

Section: A Non-linear Dynamo Modelmentioning

confidence: 99%

“…In Sraibman & Minotti (2019) the α coefficient is composed of two main additive contributions α (0) and α (1) :…”

Section: A Non-linear Dynamo Modelmentioning

confidence: 99%

“…To take a different approach to this discussion, we apply the dynamo model developed in Sraibman & Minotti (2019) to the active cool star ε Eridani and we analyzed if a solar-type dynamo model could reproduce both activity cycles reported by Metcalfe et al (2013).…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, between 1985 and 1992, the star went through a broad activity minimum, similar to the solar Maunder Minimum-state.Motivated by these results, we found in ε Eridani a great opportunity to test the dynamo theory. Based on the model developed in Sraibman & Minotti (2019), in this work we built a non linear axisymmetric dynamo for ε Eridani. The time series of the simulated magnetic field components near the surface integrated in all the stellar disc exhibits both the long and short-activity cycles with periods similar to the ones detected from observations and also time intervals of low activity which could be associated to the broad Minimun.…”

mentioning

confidence: 99%

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An application of a solar-type dynamo model for Epsilon Eridani

Buccino,

Sraibman,

Olivar

et al. 2020

Preprint

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During the last decade, the relation between activity cycle periods with stellar parameters has received special attention. The construction of reliable registries of activity reveals that solar type stars exhibit activity cycles with periods from few years to decades and, in same cases, long and short activity cycles coexist suggesting that two dynamos could operate in these stars. In particular, ε Eridani is an active young K2V star (0.8 Gyr), which exhibits a short and long-term chromospheric cycles of ∼3 and ∼13-yr periods. Additionally, between 1985 and 1992, the star went through a broad activity minimum, similar to the solar Maunder Minimum-state.Motivated by these results, we found in ε Eridani a great opportunity to test the dynamo theory. Based on the model developed in Sraibman & Minotti (2019), in this work we built a non linear axisymmetric dynamo for ε Eridani. The time series of the simulated magnetic field components near the surface integrated in all the stellar disc exhibits both the long and short-activity cycles with periods similar to the ones detected from observations and also time intervals of low activity which could be associated to the broad Minimun. The short activity cycle associated to the magnetic reversal could be explained by the differential rotation, while the long cycle is associated to the meridional mass flows induced by the Lorentz force. In this way, we show that a single non-linear dynamo model derived from first principles with accurate stellar parameters could reproduce coexisting activity cycles.

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Section: Resultsmentioning

confidence: 99%

“…In the present work we adopt the model developed in Sraibman & Minotti (2019), where magnetic feedback on the mass flow was included.…”

Section: A Non-linear Dynamo Modelmentioning

confidence: 99%

“…In Sraibman & Minotti (2019) the α coefficient is composed of two main additive contributions α (0) and α (1) :…”

Section: A Non-linear Dynamo Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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An application of a solar-type dynamo model for Epsilon Eridani

Buccino,

Sraibman,

Olivar

et al. 2020

Preprint

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Models for the long-term variations of solar activity

Karak

2023

Living Rev Sol Phys

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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 the 11-year periodicity and these include, the Gnevyshev–Ohl/Even–Odd rule, grand minima, grand maxima, Gleissberg cycle, and Suess cycles. After a brief review of the observed data, we present the dynamo models for the solar cycle. By carefully analyzing the dynamo models and the observed data, we identify the following broad causes for the modulation: (1) magnetic feedback on the flow, (2) stochastic forcing, and (3) time delays in various processes of the dynamo. To demonstrate each of these causes, we present the results from some illustrative models for the cycle modulations and discuss their strengths and weakness. We also discuss a few critical issues and their current trends. The article ends with a discussion of our current state of ignorance about comparing detailed features of the magnetic cycle and the large-scale velocity from the dynamo models with robust observations.

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Large-scale dynamo model for accretion disks

Peralta

Sraibman

Minotti

2022

A&Amp;A

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Context. Magnetic fields in accretion disks play an important role in the rich dynamics of these systems. A dynamo theory describing the generation of these magnetic field is in general very complex and requires many assumptions in order to be of practical use. In this respect, a theory with as few assumptions as possible is desirable. Aims. To investigate the generation of magnetic fields in accretion disks around magnetized central objects, a large-scale dynamo model is employed that includes feedback effects on the mass motion due to the Lorentz force. The dynamo model was developed from the fundamental magnetohydrodynamics equations with a minimum of hypothesis, and was tested in the case of the Sun and other stars. It is applied to accretion disks for the first time. Methods. The magnetic field in the disk, generated by the mentioned dynamo theory, was matched to that of the central object, considered dipolar, and to that of a magnetosphere described with the Grad-Shafranov equation. The relation between axial current and magnetic flux required in the Grad-Shafranov equation was not imposed, but was self-consistently determined along with the full solution.Results. The model is able to reproduce the patterns of magnetic field lines obtained in several works, such as closed magnetic lines near the central object and open lines for larger radii. The maximum value of the field is located near the internal radius of the accretion disk, where the currents in the disk force the concentration of field lines of the central object in the magnetosphere around this region. By varying the values of stellar mass, stellar magnetic field, mass accretion rate, and internal radius of the disk, it is found that the stellar magnetic field is the most important parameter in the determination of the disk magnetic field. The stellar mass is of secondary importance. It affects the azimuthal component of the disk magnetic field. The internal radius of the disk affects the disk zonal magnetic field and is likewise less important.

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Large-scale Model of the Axisymmetric Dynamo with Feedback Effects

Cited by 5 publications

References 48 publications

An application of a solar-type dynamo model for Epsilon Eridani

An application of a solar-type dynamo model for Epsilon Eridani

Models for the long-term variations of solar activity

Large-scale dynamo model for accretion disks

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