A solar mean field dynamo benchmark

Jouve, L.; Brun, Allan Sacha; Arlt, R.; Brandenburg, Axel; Dikpati, Mausumi; Bonanno, A.; Käpylä, Petri J.; Moss, D.; Rempel, Matthias; Gilman, Peter A.; Korpi, M. J.; Kosovichev, A. G.

doi:10.1051/0004-6361:20078351

Cited by 103 publications

(148 citation statements)

References 35 publications

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“…The rotation profile is deduced from helioseismic inversions and the α-effect is antisymmetric with respect to the equator and positive in the northern hemisphere (in agreement with the preferred handedness of the turbulent helical convective motions). This is similar to case A of Jouve et al (2008). The following values were used for the various parameters: C α = 0.385 (critical value for which dynamo action just starts to compete against Ohmic diffusion), C Ω = 1.4 × 10 5 (corresponding to a value of Ω eq = 460 nHz, in agreement with observations).…”

Section: Stelem: a Representative Dynamo Solutionsupporting

confidence: 69%

Coupling the Solar Dynamo and the Corona: Wind Properties, Mass, and Momentum Losses During an Activity Cycle

Pinto

Brun

Jouve

et al. 2011

ApJ

113

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We study the connections between the Sun's convection zone and the evolution of the solar wind and corona. We let the magnetic fields generated by a 2.5-dimensional (2.5D) axisymmetric kinematic dynamo code (STELEM) evolve in a 2.5D axisymmetric coronal isothermal magnetohydrodynamic code (DIP). The computations cover an 11 year activity cycle. The solar wind's asymptotic velocity varies in latitude and in time in good agreement with the available observations. The magnetic polarity reversal happens at different paces at different coronal heights. Overall the Sun's mass-loss rate, momentum flux, and magnetic braking torque vary considerably throughout the cycle. This cyclic modulation is determined by the latitudinal distribution of the sources of open flux and solar wind and the geometry of the Alfvén surface. Wind sources and braking torque application zones also vary accordingly.

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Section: Stelem: a Representative Dynamo Solutionsupporting

confidence: 69%

Coupling the Solar Dynamo and the Corona: Wind Properties, Mass, and Momentum Losses During an Activity Cycle

Pinto

Brun

Jouve

et al. 2011

ApJ

113

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“…This code has been thoroughly tested and validated thanks to an international mean field dynamo benchmark involving 8 different codes (Jouve et al 2008). At θ = 0 and θ = π boundaries, both A φ and B φ are set to 0.…”

Section: The Mean Field Babcock-leighton Modelmentioning

confidence: 99%

Buoyancy-induced time delays in Babcock-Leighton flux-transport dynamo models

Jouve¹,

Proctor²,

Lesur³

2010

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Context. The Sun is a magnetic star whose cyclic activity is thought to be linked to internal dynamo mechanisms. A combination of numerical modelling with various levels of complexity is an efficient and accurate tool to investigate such intricate dynamical processes. Aims. We investigate the role of the magnetic buoyancy process in 2D Babcock-Leighton dynamo models, by modelling more accurately the surface source term for poloidal field. Methods. To do so, we reintroduce in mean-field models the results of full 3D MHD calculations of the non-linear evolution of a rising flux tube in a convective shell. More specifically, the Babcock-Leighton source term is modified to take into account the delay introduced by the rise time of the toroidal structures from the base of the convection zone to the solar surface. Results. We find that the time delays introduced in the equations produce large temporal modulation of the cycle amplitude even when strong and thus rapidly rising flux tubes are considered. Aperiodic modulations of the solar cycle appear after a sequence of period doubling bifurcations typical of non-linear systems. The strong effects introduced even by small delays is found to be due to the dependence of the delays on the magnetic field strength at the base of the convection zone, the modulation being much less when time delays remain constant. We do not find any significant influence on the cycle period except when the delays are made artificially strong. Conclusions. A possible new origin of the solar cycle variability is here revealed. This modulated activity and the resulting butterfly diagram are then more compatible with observations than what the standard Babcock-Leighton model produces.

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“…The current theories assume that the poloidal component of magnetic field, which represents the global dipole field, is generated by helical turbulence at the bottom of the convection zonetachocline, and that the toroidal component, which is a source of bipolar sunspot regions, is produced by stretching the poloidal field by the differential rotation (e.g. Jouve, et al 2008). However, so far helioseismology observations were not able to confirm these models.…”

Section: Outstanding Problems Of Helioseismologymentioning

confidence: 98%

The future of helioseismology

Kosovichev¹

2009

Proc. IAU

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Abstract. Helioseismology has provided us with the unique knowledge of the interior structure and dynamics of the Sun, and the variations with the solar cycle. However, the basic mechanisms of solar magnetic activity, formation of sunspots and active regions are still unknown. Determining the physical properties of the solar dynamo, detecting emerging active regions and observing the subsurface dynamics of sunspots are among the most important and challenging problems. The current status and perspectives of helioseismology are briefly discussed.Keywords. Sun: helioseismology, activity, interior magnetic fields, oscillations, sunspots Outstanding problems of helioseismologyOne of the most important unsolved problems of solar physics and astrophysics is understanding of the physical mechanism of the dynamo operating inside the Sun and producing 11-year activity cycles. Despite a significant progress in theoretical modeling of dynamo processes and successful laboratory experiments the basic understanding of the solar dynamo is still missing. The current theories assume that the poloidal component of magnetic field, which represents the global dipole field, is generated by helical turbulence at the bottom of the convection zonetachocline, and that the toroidal component, which is a source of bipolar sunspot regions, is produced by stretching the poloidal field by the differential rotation (e.g. Jouve, et al. 2008). However, so far helioseismology observations were not able to confirm these models. If the magnetic field is generated by turbulence it is expected that when the field becomes sufficiently strong it suppresses the turbulence and affects the turbulent stresses that maintain the differential rotation. However, the helioseismic observations during a whole solar cycle were not able to detect significant variations of the rotation rate in the tachocline. They found a weak evidence of variations with a period of ∼1.3 years but no changes on the 11-year scale. In addition, to explain the emergence of magnetic fields at mid-and low latitudes the strength of the toroidal magnetic field in the tachocline must be 60-100 kG. This exceeds the energy equipartition value, and requires a dynamic compression, e.g. by back reaction of updraft motions associated with emerging magnetic flux (Parker, 2009). Such motions have not been detected by helioseismology. Alternatively, the magnetic fields can be generated in the bulk of the convection zone and shaped by the subsurface shear layer (Brandenburg, 2009). The equator-ward migration of dynamo waves in this shear layer could explain the sunspot butterfly diagram. The migrating zone of sunspot formations is associated with zonal flows ("torsional oscillations"). The magnetic flux that forms sunspots tend to emerge in the shear layer between slower and faster flows. Helioseismology has established that these flows are quite deep and occupy at least the upper 30% of the convection zone. They are particularly strong at high latitudes, where they migrate towards the poles, and pe...

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A solar mean field dynamo benchmark

Cited by 103 publications

References 35 publications

Coupling the Solar Dynamo and the Corona: Wind Properties, Mass, and Momentum Losses During an Activity Cycle

Coupling the Solar Dynamo and the Corona: Wind Properties, Mass, and Momentum Losses During an Activity Cycle

Buoyancy-induced time delays in Babcock-Leighton flux-transport dynamo models

The future of helioseismology

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