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We explore effects of random non-axisymmetric perturbations of kinetic helicity (the $alpha$ effect) and diffusive decay of bipolar magnetic regions on generation and evolution of large-scale non-axisymmetric magnetic fields on the Sun. Using a reduced 2D nonlinear mean-field dynamo model and assuming that bipolar regions emerge due to magnetic buoyancy in situ of the large-scale dynamo action, we show that fluctuations of the $alpha$ effect can maintain the non-axisymmetric magnetic fields through a solar-type $alpha^{2}Omega$ dynamo process. It is found that diffusive decay of bipolar active regions is likely to be the primary source of the non-axisymmetric magnetic fields observed on the Sun. Our results show that the non-axisymmetric dynamo model with stochastic perturbations of the $alpha$ effect can explain periods of extremely high activity (`super-cycle events) as well as periods of deep decline of magnetic activity. We compare the models with synoptic observations of solar magnetic fields for the last four activity cycles, and discuss implications of our results for interpretation of observations of stellar magnetic activity.
In the quiet Sun, magnetic fields are usually observed as small-scale magnetic elements, `salt and pepper, covering the entire solar surface. By using 3D radiative MHD numerical simulations we demonstrate that these fields are a result of local dynam
We seek to understand the transition from nearly axisymmetric configurations at solar rotation rates to nonaxisymmetric configurations for rapid rotation using 3D numerical simulations of turbulent convection and considering rotation rates between 1
Magnetic fields are usually observed in the quiet Sun as small-scale elements that cover the entire solar surface (the `salt and pepper patterns in line-of-sight magnetograms). By using 3D radiative MHD numerical simulations we find that these fields
Sunspots are cool areas caused by strong surface magnetic fields inhibiting convection. Moreover, strong magnetic fields can alter the average atmospheric structure, degrading our ability to measure stellar masses and ages. Stars more active than the
The Stellar Imager mission concept is a space-based UV/Optical interferometer designed to resolve surface magnetic activity and subsurface structure and flows of a population of Sun-like stars, in order to accelerate the development and validation of