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We present the first model that couples the formation of the corona of a solar active region to a model of the emergence of a sunspot pair. This allows us to study when, where, and why active region loops form, and how they evolve. We use a…

Solar and Stellar Astrophysics · Physics 2014-05-08 F. Chen , H. Peter , S. Bingert , M. C. M. Cheung

Observations suggest a power-law relation between the coronal emission in X-rays, $L_{\rm{X}}$, and the total (unsigned) magnetic flux at the stellar surface, $\Phi$. The physics basis for this relation is poorly understood. We use…

Solar and Stellar Astrophysics · Physics 2021-08-04 J. Zhuleku , J. Warnecke , H. Peter

Thermal conductivity is one of the important mechanisms of heat transfer in the solar corona. In the limit of strongly magnetized plasma, it is typically modeled by Spitzer's expression where the heat flux is aligned with the magnetic…

Solar and Stellar Astrophysics · Physics 2022-07-20 Anamaría Navarro , E. Khomenko , M. Modestov , N. Vitas

The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that…

The chromosphere of the quiet Sun is a highly intermittent and dynamic phenomenon. Three-dimensional radiation (magneto-)hydrodynamic simulations exhibit a mesh-like pattern of hot shock fronts and cool expanding post-shock regions in the…

Astrophysics · Physics 2009-11-13 Sven Wedemeyer-Böhm , Friedrich Wöger

We model the hydrodynamic evolution of the plasma confined in a coronal loop, 30000 km long, subject to the heating of nanoflares due to intermittent magnetic dissipative events in the MHD turbulence produced by loop footpoint motions. We…

Astrophysics · Physics 2009-11-13 F. Reale , G. Nigro , F. Malara , G. Peres , P. Veltri

The dynamical coupling between the solar chromospheric plasma and magnetic field is investigated by numerically solving a fully self-consistent, two-dimensional initial-value problem for the nonlinear collisional MHD equations including…

Solar and Stellar Astrophysics · Physics 2015-12-09 L. M. Alekseeva , S. P. Kshevetskii

We study extreme-ultraviolet emission line spectra derived from three-dimensional magnetohydrodynamic models of structures in the corona. In order to investigate the effects of increased magnetic activity at photospheric levels in a…

Solar and Stellar Astrophysics · Physics 2009-04-16 Pia Zacharias , Sven Bingert , Hardi Peter

Twisted magnetic fields should be ubiquitous in flare-producing active regions where the magnetic fields are strongly non-potential. It has been shown that reconnection in helical magnetic coronal loops results in plasma heating and…

Solar and Stellar Astrophysics · Physics 2016-01-20 R. F. Pinto , M. Gordovskyy , P. K. Browning , N. Vilmer

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

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 representing a quiet region and a plage region, respectively,…

Solar and Stellar Astrophysics · Physics 2015-06-03 R. Moll , R. H. Cameron , M. Schüssler

Over the last decades, realistic 3D radiative-MHD simulations have become the dominant theoretical tool for understanding the complex interactions between the plasma and the magnetic field on the Sun. Most of such simulations are based on…

Solar and Stellar Astrophysics · Physics 2018-10-17 E. Khomenko , N. Vitas , M. Collados , A. de Vicente

We present a detailed analysis of a 3D MHD simulation of a subset of the magnetic flux in an active region. The simulation models the generation of nanoflares and response of the plasma to imposed photospheric motions. Our study focuses on…

Solar and Stellar Astrophysics · Physics 2025-09-26 Shanwlee Sow Mondal , Lars K. S. Daldorff , James A. Klimchuk , Craig D. Johnston

This work analyzes the Hall magnetohydrodynamics (HMHD) and magnetohydrodynamics (MHD) numerical simulations of a flaring solar active region as a testbed while idealizing the coronal Alfv\'en speed to be of two orders of magnitude lesser.…

Solar and Stellar Astrophysics · Physics 2022-02-16 Kamlesh Bora , Ramit Bhattacharyya , Avijeet Prasad , Bhuwan Joshi , Qiang Hu

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

The distribution of temperature and emission measure in the stationary heated solar atmosphere was obtained for the limiting cases of slow and fast heating, when either the gas pressure or the concentration are constant throughout the layer…

Solar and Stellar Astrophysics · Physics 2010-04-16 O. Ptitsyna , B. Somov

A simplified non-linear numerical model for the development of incompressible magnetohydrodynamics (MHD) in the presence of a strong magnetic field B0 and stratification, nicknamed Shell-Atm, is presented. In planes orthogonal to the mean…

Astrophysics · Physics 2011-02-11 E. Buchlin , M. Velli

The solar atmosphere is known to contain many different types of wavelike oscillation. Waves and other fluctuations (e.g., turbulent eddies) are believed to be responsible for at least some of the energy transport and dissipation that heats…

Solar and Stellar Astrophysics · Physics 2023-08-09 Steven R. Cranmer , Momchil E. Molnar

MHD waves permeate the solar atmosphere and constitute potential coronal heating agents. Yet, the waves detected so far may be but a small subset of the true existing wave power. Detection is limited by instrumental constraints, but also by…

Solar and Stellar Astrophysics · Physics 2017-02-03 Patrick Antolin , Ineke De Moortel , Tom Van Doorsselaere , Takaaki Yokoyama

The solar corona, the tenuous outer atmosphere of the Sun, is orders of magnitude hotter than the solar surface. This 'coronal heating problem' requires the identification of a heat source to balance losses due to thermal conduction,…

Solar and Stellar Astrophysics · Physics 2015-10-06 Ineke De Moortel , Philippa Browning