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Magnetic features on the surfaces of cool stars cause variations of their brightness. Such variations have been extensively studied for the Sun. Recent planet-hunting space telescopes allowed measuring brightness variations in hundred…

Solar and Stellar Astrophysics · Physics 2020-04-15 N. -E. Nèmec , A. I. Shapiro , N. A. Krivova , S. K. Solanki , R. V. Tagirov , R. H. Cameron , S. Dreizler

Convection is one of the most important mixing processes in stellar interiors. Hydrodynamic mass entrainment can bring fresh fuel from neighboring stable layers into a convection zone, modifying the structure and evolution of the star.…

Solar and Stellar Astrophysics · Physics 2023-11-29 G. Leidi , R. Andrassy , J. Higl , P. V. F. Edelmann , F. K. Röpke

The role of diffuse photospheric magnetic elements in the energy budget of the upper layers of the Sun's atmosphere has been the recent subject of many studies. This was made possible by the availability of high temporal and spatial…

Solar and Stellar Astrophysics · Physics 2014-10-01 M. Stangalini , G. Consolini , F. Berrilli , P. De Michelis , R. Tozzi

The present-day abundance of beryllium in the solar atmosphere provides clues about mixing mechanisms within stellar interiors. However, abundance determinations based on the Be II 313.107 nm line are prone to systematic errors due to…

Solar and Stellar Astrophysics · Physics 2024-09-09 A. M. Amarsi , D. Ogneva , G. Buldgen , N. Grevesse , Y. Zhou , P. S. Barklem

We characterize the 3-D spatial variations of [Fe/H], [Mg/H], and [Mg/Fe] in stars at the time of their formation, across 11 simulated Milky Way (MW)- and M31-mass galaxies in the FIRE-2 simulations, to inform initial conditions for…

Astrophysics of Galaxies · Physics 2022-06-22 Matthew A. Bellardini , Andrew Wetzel , Sarah R. Loebman , Jeremy Bailin

Aims. Moreno-Insertis et al. (2018) recently discovered two types of flux emergence in their numerical simulations: magnetic loops and magnetic sheet emergence. Whereas magnetic loop emergence has been documented well in the last years, by…

Solar and Stellar Astrophysics · Physics 2019-02-13 C. E. Fischer , J. M. Borrero , N. Bello González , A. J. Kaithakkal

We study the impact of new metallicity measurements, from solar wind data, on the solar model. The "solar modelling problem" refers to the persisting discrepancy between helioseismological observations and predictions of solar models…

Solar and Stellar Astrophysics · Physics 2017-04-14 Sunny Vagnozzi , Katherine Freese , Thomas H. Zurbuchen

A comprehensive understanding of the solar magnetic cycle requires detailed modeling of the solar interior including the maintenance and variation of large scale flows (differential rotation and meridional flow), the solar dynamo and the…

Solar and Stellar Astrophysics · Physics 2010-10-29 M. Rempel

On the basis of Stokes parameter calculations for the Fe I 524.7 and 525.0 nm lines and the Holweger-Muller model atmosphere, the effect of the anomalous dispersion on solar magnetic field measurements by the line-ratio method is analyzed.…

Solar and Stellar Astrophysics · Physics 2021-12-09 V. G. Lozitskii , V. A. Sheminova

We investigate numerically magnetic field generation by thermal convection with square periodicity cells in a rotating horizontal layer of electrically-conducting fluid with stress-free electrically perfectly conducting boundaries for…

Chaotic Dynamics · Physics 2010-04-12 V. Zheligovsky

Aims: To investigate magnetic reconnection rates during the coalescence of two current loops in the solar chromosphere, by altering the neutral-hydrogen to proton density ratio, ioniziation/recombination coefficients, collision frequency…

Astrophysics · Physics 2009-11-13 P. D. Smith , J. I. Sakai

We review recent insights into the dynamics of the solar convection zone obtained from global numerical simulations, focusing on two recent developments in particular. The first is quasi-cyclic magnetic activity in a long-duration dynamo…

Solar and Stellar Astrophysics · Physics 2015-05-20 Mark S. Miesch , Benjamin P. Brown , Matthew K. Browning , Allan Sacha Brun , Juri Toomre

In network and active region plages, the magnetic field is concentrated into structures often described as flux tubes (FTs) and sheets (FSs). 3-D radiative transfer (RT) is important for energy transport in these concentrations. It is also…

Solar and Stellar Astrophysics · Physics 2015-06-11 R. Holzreuter , S. K. Solanki

This paper describes a series of 3D simulations of shallow inefficient convection in the outer layers of the Sun. The computational domain is a closed box containing the convection-radiation transition layer, located at the top of the solar…

Astrophysics · Physics 2009-11-07 F. J. Robinson , P. Demarque , L. H. Li , S. Sofia , Y. -C. Kim , K. L. Chan , D. B. Guenther

Oxygen is a powerful tracer element of Galactic chemical evolution. Unfortunately, only a few oxygen lines are available in the ultraviolet-infrared stellar spectra for the reliable determination of its abundance. Moreover, oxygen…

Solar and Stellar Astrophysics · Physics 2014-09-11 A. Kucinskas , V. Dobrovolskas , P. Bonifacio , E. Caffau , H. -G. Ludwig , M. Steffen , M. Spite

Advances in hydrodynamical simulations have provided new insights into the effects of convection on the frequencies of solar oscillations. As more accurate observations become available, this may lead to an improved understanding of the…

Chromospheric observations of sunspot umbrae offer an exceptional view of magneto-acoustic shock phenomena and the impact they have on the surrounding magnetically-dominated plasma. We employ simultaneous slit-based spectro-polarimetry and…

Solar and Stellar Astrophysics · Physics 2018-06-13 S. J. Houston , D. B. Jess , A. Asensio Ramos , S. D. T. Grant , C. Beck , A. A. Norton , S. Krishna Prasad

Sunspots and active regions observed on the solar surface are widely believed to be manifestations of compact predominantly-toroidal magnetic field structures (``flux tubes") that emerge by magnetic buoyancy from the deeper interior of the…

Solar and Stellar Astrophysics · Physics 2024-06-21 Bhishek Manek , Nicholas Brummell

We show that standard solar models are in good agreement with the helioseismologically determined sound speed and density as a function of solar radius, the depth of the convective zone, and the surface helium abundance, as long as those…

Astrophysics · Physics 2011-09-29 John N. Bahcall , Sarbani Basu , Marc Pinsonneault , Aldo M. Serenelli

We investigate the evolution of both normal and inverse CMEs ejected at different initial velocities, and observe the effect of the background wind density and their magnetic polarity on their evolution up to 1 AU. We performed 2.5D…

Solar and Stellar Astrophysics · Physics 2019-10-11 S. Hosteaux , E. Chané , S. Poedts