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Observationally guided models for the solar dynamo and the role of the surface field
Robert Cameron, Manfred Schüssler
Theoretical models for the solar dynamo range from simple low-dimensional ``toy models'' to complex 3D-MHD simulations. Here we mainly discuss appproaches that are motivated and gu…
No evidence for synchronization of the solar cycle by a "clock"
E. Weisshaar, R. H. Cameron, M. Schüssler
The length of the solar activity cycle fluctuates considerably. The temporal evolution of the corresponding cycle phase, that is, the deviation of the epochs of activity minima or…
An update of Leighton's solar dynamo model
R. H. Cameron, M. Schuessler
In 1969 Leighton developed a quasi-1D mathematical model of the solar dynamo, building upon the phenomenological scenario of Babcock(1961). Here we present a modification and exten…
Solar magnetoconvection and small-scale dynamo: Recent developments in observation and simulation
J. M. Borrero, S. Jafarzadeh, M. Schüssler +1
A number of observational and theoretical aspects of solar magnetoconvection are considered in this review. We discuss recent developments in our understanding of the small-scale s…
The cause of the weak solar cycle 24
Jie Jiang, Robert H. Cameron, Manfred Schuessler
The ongoing 11-year cycle of solar activity is considerably less vigorous than the three cycles before. It was preceded by a very deep activity minimum with a low polar magnetic fl…
Three-dimensional simulations of near-surface convection in main-sequence stars. IV. Effect of small-scale magnetic flux concentrations on centre-to-limb variation and spectral lines
Benjamin Beeck, Manfred Schüssler, Robert H. Cameron +1
Magnetic fields affect the local structure of the photosphere of stars. They can considerably influence the radiative properties near the optical surface, flow velocities, and the…
Three-dimensional simulations of near-surface convection in main-sequence stars. III. The structure of small-scale magnetic flux concentrations
Benjamin Beeck, Manfred Schüssler, Robert H. Cameron +1
The convective envelopes of cool main-sequence stars harbour magnetic fields with a complex global and local structure. These fields affect the near-surface convection and the oute…
Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
A. Reiners, M. Schuessler, V. M. Passegger
Magnetic activity in Sun-like and low-mass stars causes X-ray coronal emission, which is stronger for more rapidly rotating stars. This relation is often interpreted in terms of th…
MHD simulations of near-surface convection in cool main-sequence stars
Benjamin Beeck, Manfred Schüssler, Ansgar Reiners
The solar photospheric magnetic field is highly structured owing to its interaction with the convective flows. Its local structure has a strong influence on the profiles of spectra…
Comparison of solar photospheric bright points between SUNRISE observations and MHD simulations
T. L. Riethmüller, S. K. Solanki, S. V. Berdyugina +5
Bright points (BPs) in the solar photosphere are radiative signatures of magnetic elements described by slender flux tubes located in the darker intergranular lanes. They contribut…
Effects of the scatter in sunspot group tilt angles on the large-scale magnetic field at the solar surface
J. Jiang, R. H. Cameron, M. Schuessler
The tilt angles of sunspot groups represent the poloidal field source in Babcock-Leighton-type models of the solar dynamo and are crucial for the build-up and reversals of the pola…
Three-dimensional simulations of near-surface convection in main-sequence stars - I. Overall structure
Benjamin Beeck, Robert H. Cameron, Ansgar Reiners +1
The near-surface layers of cool main-sequence stars are structured by convective flows, which are overshooting into the atmosphere. The flows and the associated spatio-temporal var…
Three-dimensional simulations of near-surface convection in main-sequence stars - II. Properties of granulation and spectral lines
Benjamin Beeck, Robert H. Cameron, Ansgar Reiners +1
The atmospheres of cool main-sequence stars are structured by convective flows from the convective envelope that penetrate the optically thin layers and lead to structuring of the…
Limits to solar cycle predictability: Cross-equatorial flux plumes
R. H. Cameron, M. Dasi-Espuig, J. Jiang +3
Within the Babcock-Leighton framework for the solar dynamo, the strength of a cycle is expected to depend on the strength of the dipole moment or net hemispheric flux during the pr…
Solar magneto-convection
Manfred Schüssler
An overview is given about recent developments and results of comprehensive simulations of magneto-convective processes in the near-surface layers and photosphere of the Sun. Simul…
Modelling stellar activity cycles using deep-seated dynamos and surface flux transport
Emre Işik, Dieter Schmitt, Manfred Schüssler
We investigate the relations between tachocline-based dynamos and the surface flux transport mechanisms in stars with outer convection zones. Using our combined models of flux gene…
Are the strengths of solar cycles determined by converging flows towards the activity belts?
R. H. Cameron, M. Schuessler
It is proposed that the observed near-surface inflows towards the active regions and sunspot zones provide a nonlinear feedback mechanism that limits the amplitude of a Babcock-Lei…
Simulations of the solar near-surface layers with the CO5BOLD, MURaM, and Stagger codes
B. Beeck, R. Collet, M. Steffen +6
Radiative hydrodynamic simulations of solar and stellar surface convection have become an important tool for exploring the structure and gas dynamics in the envelopes and atmospher…
Vortices, shocks, and heating in the solar photosphere: effect of a magnetic field
R. Moll, R. H. Cameron, M. Schüssler
Aims: We study the differences between non-magnetic and magnetic regions in the flow and thermal structure of the upper solar photosphere. Methods: Radiative MHD simulations repres…
A coupled model of magnetic flux generation and transport in stars
Emre Işık, Dieter Schmitt, Manfred Schüssler
We present a combined model for magnetic field generation and transport in cool stars with outer convection zones. The mean toroidal magnetic field, which is generated by a cyclic…
Decay of a simulated mixed-polarity magnetic field in the solar surface layers
Robert Cameron, Alexander Voegler, Manfred Schuessler
Magnetic flux is continuously being removed and replenished on the solar surface. To understand the removal process we carried out 3D radiative MHD simulations of the evolution of…
Vortices in simulations of solar surface convection
R. Moll, R. H. Cameron, M. Schüssler
We report on the occurrence of small-scale vortices in simulations of the convective solar surface. Using an eigenanalysis of the velocity gradient tensor, we find the subset of hi…
Can overturning motions in penumbral filaments be detected?
Lokesh Bharti, Manfred Schuessler, Matthias Rempel
Numerical simulations indicate that the filamentation of sunspot penumbrae and the associated systematic outflow (the Evershed effect) are due to convectively driven fluid motions…
Can surface flux transport account for the weak polar field in cycle 23?
Jie Jiang, Robert H. Cameron, Dieter Schmitt +1
To reproduce the weak magnetic field on the polar caps of the Sun observed during the declining phase of cycle 23 poses a challenge to surface flux transport models since this cycl…