Solar Dynamics, Rotation, Convection and Overshoot

Hanasoge, Shravan M.; Miesch, Mark S.; Roth, Markus; Schou, J.; Schüßler, M.; Thompson, M. J.

doi:10.1007/s11214-015-0144-0

Cited by 25 publications

(22 citation statements)

References 111 publications

(117 reference statements)

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“…The most ambitious of these studies that have so far appeared do indeed succeed in reproducing cyclic magnetic activity, together with meridional velocities that have a complicated, time-dependent structure. At high latitudes there is an equatorward flow at the tachocline, with poleward motion in most of the convection zone, giving way to equatorward flow above 0.9R⊙ and rapid poleward velocities nearer to the surface (Passos, Charbonneau & Miesch 2015;Hanasoge et al 2015). The corresponding azimuthal fields accumulate near the tachocline and display dipole symmetry; they reverse cyclically and have been followed for 40 activity cycles, with an average period of 40 years (Passos & Charbonneau 2014;Passos, Charbonneau & Miesch 2015).…”

Section: Super-modulation and Symmetry Changes In The Solar Dynamomentioning

confidence: 99%

Supermodulation of the Sun's magnetic activity: the effects of symmetry changes

Weiss¹,

Tobias²

2015

Mon. Not. R. Astron. Soc.

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In this paper we argue that the solar activity record, as revealed by telescopic observations and proxy data from the abundances of cosmogenic isotopes, is consistent with the action of a deterministic nonlinear chaotic dynamo. In particular we claim that the long timescale 'super-modulation' apparent in the isotopic record can be ascribed to switching of the dynamo between two different modulational patterns. The first (which is currently in operation) involves deep grand minima and occasional changes in symmetry triggered by these minima. The second, which exhibits only weak modulation and no grand minima, arises as a consequence of symmetry breaking. These processes are demonstrated for highly idealized simple models of the nonlinear dynamo equations.

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Section: Super-modulation and Symmetry Changes In The Solar Dynamomentioning

confidence: 99%

Supermodulation of the Sun's magnetic activity: the effects of symmetry changes

Weiss¹,

Tobias²

2015

Mon. Not. R. Astron. Soc.

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“…Interestingly, these simulation results also indicate that the Sun may be near the tipping point between these two rotational regimes. It must be noted however that the limited range of spatial scales in numerical simulations may lead one to over-estimate the amplitude of convective flows (see Hanasoge et al 2015;Greer et al 2015 and references therein), which would in turn change the critical stellar Rossby number at which this transition occur. One could nevertheless infer from these simulation results that a simple, monotonic relationship between cycle and rotation periods is not to be expected, considering that differential rotation is a key inductive process in the vast majority of extant solar/stellar dynamo scenarios.…”

Section: Introductionmentioning

confidence: 99%

On the Sensitivity of Magnetic Cycles in Global Simulations of Solar-like Stars

Strugarek

Beaudoin

Charbonneau

et al. 2018

ApJ

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The periods of magnetic activity cycles in the Sun and solar-type stars do not exhibit a simple or even single trend with respect to rotation rate or luminosity. Dynamo models can be used to interpret this diversity, and can ultimately help us understand why some solar-like stars do not exhibit a magnetic cycle, whereas some do, and for the latter what physical mechanisms set their magnetic cycle period. Three-dimensional non-linear magnetohydrodynamical simulations present the advantage of having only a small number of tunable parameters, and produce in a dynamically self-consistent manner the flows and the dynamo magnetic fields pervading stellar interiors. We conducted a series of such simulations within the EULAG-MHD framework, varying the rotation rate and luminosity of the modeled solar-like convective envelopes. We find decadal magnetic cycles when the Rossby number near the base of the convection zone is moderate (typically between 0.25 and 1). Secondary, shorter cycles located at the top of the convective envelope close to the equator are also observed in our numerical experiments, when the local Rossby number is lower than 1. The deep-seated dynamo sustained in these numerical experiments is fundamentally non-linear, in that it is the feedback of the large-scale magnetic field on the large-scale differential rotation that sets the magnetic cycle period. The cycle period is found to decrease with the Rossby number, which offers an alternative theoretical explanation to the variety of activity cycles observed in solar-like stars.

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“…The matter was first seriously considered by Spiegel andZahn (1992, see also Spiegel (1972)). They, like I here, did not discuss the cause of differential rotation of the convection zone: it is evidently the result of a balance between the angular-momentum-transporting Reynolds stress, Maxwell stress and advection by large-scale meridional flow, a matter which is reviewed briefly by Hanasoge et al (2015) in this volume. Instead, recognizing that the global equilibration timescale of convection is no doubt much shorter than the dynamical timescales of processes operating beneath (even if they are related to the solar cycle), Spiegel and Zahn considered the convection-zone shear to be given, and ignored any back-reaction of the tachocline dynamics on the convection zone.…”

Section: The Steady Laminar Tachoclinementioning

confidence: 94%

Some Glimpses from Helioseismology at the Dynamics of the Deep Solar Interior

Gough¹

2017

Space Sciences Series of ISSI

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Helioseismology has taught us a great deal about the stratification and kinematics of the solar interior, sufficient for us to embark upon dynamical studies more detailed than have been possible before. The most sophisticated studies to date have been the very impressive numerical simulations of the convection zone, from which, especially in recent years, a great deal has been learnt. Those simulations, and the seismological evidence with which they are being confronted, are reviewed elsewhere in this volume. Our understanding of the global dynamics of the radiative interior of the Sun is in a much more primitive state. Nevertheless, some progress has been made, and seismological inference has provided us with evidence of more to come. Some of that I summarize here, mentioning in passing hints that are pointing the way to the future.

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Solar Dynamics, Rotation, Convection and Overshoot

Cited by 25 publications

References 111 publications

Supermodulation of the Sun's magnetic activity: the effects of symmetry changes

Supermodulation of the Sun's magnetic activity: the effects of symmetry changes

On the Sensitivity of Magnetic Cycles in Global Simulations of Solar-like Stars

Some Glimpses from Helioseismology at the Dynamics of the Deep Solar Interior

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