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Three-dimensional magnetohydrodynamic simulations of the surface layers of the Sun intrinsically produce a predominantly horizontal magnetic field in the photosphere. This is a robust result in the sense that it arises from simulations with…

Solar and Stellar Astrophysics · Physics 2009-04-15 O. Steiner , R. Rezaei , R. Schlichenmaier , W. Schaffenberger , S. Wedemeyer-Böhm

Abridged: Recent simulations have explored different ways to form accretion disks around low-mass stars. We aim to present observables to differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded…

Solar and Stellar Astrophysics · Physics 2015-04-29 Daniel Harsono , Ewine van Dishoeck , Simon Bruderer , Zhi-Yun Li , Jes Jorgensen

The Ca II H & K lines are strong chromospheric diagnostics that can be used to determine the temperature stratification and magnetic structure of the solar atmosphere. The Atacama Large Millimetre/Submillimetre Array (ALMA) offers…

Solar and Stellar Astrophysics · Physics 2024-05-09 Sneha Pandit , Sven Wedemeyer , Mats Carlsson

CO is the most widely used observational tracer of molecular gas. The observable CO luminosity is translated to H_2 mass via a conversion factor, X_CO, which is a source of uncertainty and bias. Despite variations in X_CO, the…

Astrophysics of Galaxies · Physics 2020-11-18 Munan Gong , Eve C. Ostriker , Chang-Goo Kim , Jeong-Gyu Kim

Turbulent diffuse molecular clouds can exhibit complicated morphologies caused by the interactions among radiation, chemistry, fluids, and fields. We performed full 3D simulations for turbulent diffuse molecular interstellar media,…

Astrophysics of Galaxies · Physics 2024-07-17 Nannan Yue , Lile Wang , Thomas Bisbas , Donghui Quan , Di Li

The distribution and evolution of the magnetic field at the solar poles through a solar cycle is an important parameter in understanding the solar dynamo. The accurate observations of the polar magnetic flux is very challenging from the…

Solar and Stellar Astrophysics · Physics 2024-07-26 Sanjay Gosain , Han Uitenbroek

We study the observational signature of flux emergence in the photosphere using synthetic data from a 3D MHD simulation of the emergence of a twisted flux tube. Several stages in the emergence process are considered. At every stage we…

Solar and Stellar Astrophysics · Physics 2015-05-14 L. Yelles Chaouche , M. C. M. Cheung , S. K. Solanki , M. Schuessler , A. Lagg

We derive formulae connecting the frequency variations in the spectrum of solar oscillations to the dynamical quantities that are expected to change over the solar activity cycle. This is done for both centroids and the asymmetric part of…

Astrophysics · Physics 2009-11-10 W. A. Dziembowski , P. R. Goode

Continuum intensity observations obtained with the Michelson Doppler Imager (MDI) on-board the SoHO mission provide long time series of filtergrams that are ideal for studying the evolution of large-scale phenomena in the solar atmosphere…

Solar and Stellar Astrophysics · Physics 2015-05-20 S. Criscuoli , I. Ermolli , D. Del Moro , F. Giorgi , A. Tritschler , H. Uitenbroek , N. Vitas

The Millimeter-wave Intensity Mapping Experiment (mmIME) recently reported a detection of excess spatial fluctuations at a wavelength of 3 mm, which can be attributed to unresolved emission of several CO rotational transitions between…

Cosmology and Nongalactic Astrophysics · Physics 2022-04-20 Patrick C. Breysse , Shengqi Yang , Rachel S. Somerville , Anthony R. Pullen , Gergö Popping , Abhishek S. Maniyar

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

Using numerical simulations, we study the formation and dynamics of post-flare loops in a local region of the solar atmosphere. The MHD equations rule the post-flare structures' dynamic evolution, including space-dependent magnetic…

Solar and Stellar Astrophysics · Physics 2024-02-15 Mauricio González-Servín , J. J. González-Avilés

Magnetohydrodynamic (MHD) turbulence in the solar wind is observed to show the spectral behavior of classical Kolmogorov fluid turbulence over an inertial subrange and departures from this at short wavelengths, where energy should be…

Space Physics · Physics 2009-11-11 S. D. Bale , P. J. Kellogg , F. S. Mozer , T. S. Horbury , H. Reme

Radiative turbulent mixing layers are expected to form pervasively at the phase boundaries in multiphase astrophysical systems. This inherently small scale structure is dynamically crucial because it directly regulates the mass, momentum…

Astrophysics of Galaxies · Physics 2023-10-04 Xihui Zhao , Xue-Ning Bai

We study the properties of solar magnetic fields on scales less than the spatial resolution of solar telescopes. A synthetic infrared spectropolarimetric diagnostics based on a 2D MHD simulation of magnetoconvection is used for this. We…

Solar and Stellar Astrophysics · Physics 2009-02-10 V. A. Sheminova

Convective motions at the stellar surface generate a stochastic colored noise source in the radial velocity (RV) data. This noise impedes the detection of small exoplanets. Moreover, the unknown statistics (amplitude, distribution) related…

Earth and Planetary Astrophysics · Physics 2020-04-01 S. Sulis , D. Mary , L. Bigot

In the recent years, global coronal models have experienced an ongoing increase in popularity as tools for forecasting solar weather. Within the domain of up to 21.5Rsun, magnetohydrodynamics (MHD) is used to resolve the coronal structure…

Solar and Stellar Astrophysics · Physics 2022-11-30 Michaela Brchnelova , Błażej Kuźma , Barbara Perri , Andrea Lani , Stefaan Poedts

In this study we investigate the effects of turbulent convection on formation of large-scale inhomogeneous magnetic structures by means of Large-Eddy Simulation (LES) for convection in solar-type stars. The main idea of this study is the…

Solar and Stellar Astrophysics · Physics 2011-02-08 I. Rogachevskii , N. Kleeorin , I. N. Kitiashvili , A. G. Kosovichev , A. A. Wray , N. N. Mansour

Aims: we seek to provide additional tests of the line formation of theoretical 3D solar photosphere models. In particular, we set out to test the spatially-resolved line formation at several viewing angles, from the solar disk-centre to the…

Solar and Stellar Astrophysics · Physics 2015-05-14 Tiago M. D. Pereira , Dan Kiselman , Martin Asplund

Solar flares are intense bursts of electromagnetic radiation, which occur due to a rapid destabilization and reconnection of the magnetic field. While pre-flare signatures and trends have been investigated from magnetic observations prior…

Solar and Stellar Astrophysics · Physics 2025-06-18 Kara L. Kniezewski , Emily I. Mason , Daniel J. Emmons , Kyle E. Fitch , Seth H. Garland