scholarly journals Radiation hydrodynamics in simulations of the solar atmosphere

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Jorrit Leenaarts
Keyword(s):  
Radiation Field ◽  
Solar Atmosphere ◽  
Energy Exchange ◽  
Atmospheric Modeling ◽  
Radiation Hydrodynamics ◽  
Essential Ingredient ◽  
Approximate Form ◽  
Mhd Modeling ◽  
Computationally Expensive

AbstractNearly all energy generated by fusion in the solar core is ultimately radiated away into space in the solar atmosphere, while the remaining energy is carried away in the form of neutrinos. The exchange of energy between the solar gas and the radiation field is thus an essential ingredient of atmospheric modeling. The equations describing these interactions are known, but their solution is so computationally expensive that they can only be solved in approximate form in multi-dimensional radiation-MHD modeling. In this review, I discuss the most commonly used approximations for energy exchange between gas and radiation in the photosphere, chromosphere, and corona.

Realistic 3D MHD modeling of self-organized magnetic structuring of the solar corona

2019 ◽  
Vol 15 (S354) ◽  
pp. 346-350
Author(s):  
Irina N. Kitiashvili ◽  
Alan A. Wray ◽  
Viacheslav Sadykov ◽  
Alexander G. Kosovichev ◽  
Nagi N. Mansour
Keyword(s):  
Energy Exchange ◽  
Solar Surface ◽  
Solar Interior ◽  
Spatial And Temporal Scales ◽  
Atmospheric Processes ◽  
Complex Interactions ◽  
Self Organized ◽  
Mhd Simulations ◽  
Wide Range ◽  
Mhd Modeling

AbstractThe dynamics of solar magnetoconvection spans a wide range of spatial and temporal scales and extends from the interior to the corona. Using 3D radiative MHD simulations, we investigate the complex interactions that drive various phenomena observed on the solar surface, in the low atmosphere, and in the corona. We present results of our recent simulations of coronal dynamics driven by underlying magnetoconvection and atmospheric processes, using the 3D radiative MHD code StellarBox (Wray et al. 2018). In particular, we focus on the evolution of thermodynamic properties and energy exchange across the different layers from the solar interior to the corona.

scholarly journals Radiative Damping of Gravity Waves in the Solar Atmosphere

1980 ◽  
Vol 58 ◽  
pp. 301-306
Author(s):  
Jerry D. Logan ◽  
Henry A. Hill
Keyword(s):  
Radiation Field ◽  
Solar Atmosphere ◽  
Gravity Waves ◽  
Driving Mechanism ◽  
Solar Photosphere ◽  
Nonlocal Effects ◽  
Newtonian Approximation ◽  
Radiative Damping ◽  
Low Order

AbstractThe nonlocal character of the radiation field sinnificantly modifies the radiative damping of perturbations in the solar photosphere. Gravity waves are not usually considered to exist in the solar photosphere because the radiative damping time, when based on the Newtonian approximation, is too short. However, this restriction does not apply to low order gravity waves. In fact, with the inclusion of nonlocal effects, the radiative damping for low order gravity waves becomes negative for some region in the photosphere and thus acts as a driving mechanism for gravity waves there.

scholarly journals Radiation Hydrodynamics in Pulsating Stars

1986 ◽  
Vol 89 ◽  
pp. 36-52
Author(s):  
Robert F. Stellingwerf
Keyword(s):  
Velocity Field ◽  
Radiation Field ◽  
Thermal Effects ◽  
Nonlinear Effects ◽  
Time Dependent ◽  
Radiation Hydrodynamics ◽  
Current Interest ◽  
Dynamic Effects ◽  
Pulsating Stars ◽  
Stellar Stability

The topic of this review encompasses all aspects of pulsation theory, for the radiation field is never negligible in stellar stability problems, on the contrary, it is usually the primary destabilizing factor through its thermal effects, and modifies the envelope structure and stability through its dynamic effects. The impossibility of a general review of such a broad topic is apparent, and I will concentrate in this talk on the most striking aspect of pulsating stars: nonlinear effects in the outer layers. To focus the discussion, I will address primarily two problems of current interest: shock development driven by the pulsating velocity field, and time dependent turbulence in the ionization zones. The emphasis will be on methodology rather than specific problems and developments.

scholarly journals Introduction and Overview

1986 ◽  
Vol 89 ◽  
pp. 1-4 ◽  
Author(s):  
Dimitri Mihalas
Keyword(s):  
Solar System ◽  
Radiation Field ◽  
Diagnostic Tool ◽  
Rapid Development ◽  
Physical Structure ◽  
Radiation Hydrodynamics ◽  
Diagnostic Problem ◽  
Polarization Variation

The theme of this Colloquium is radiation hydrodynamics in and around stars and other compact bodies. To open our discussions, I would like to offer some rather elementary remarks about the role played by radiation in astrophysics.It is probably true that most astronomers view radiation primarily as a diagnostic tool. After all, the only access we have to astrophysical bodies (with a few exceptions inside the Solar System) is the photons we capture from them. And so an immense effort has been devoted to the development of techniques for converting raw information about the spatial, temporal, spectral, and polarization variation of the observed radiation field into knowledge about the physical structure of the object that produced the radiation. There are many difficult challenges, both observational and theoretical, to be met in this process, and the field is in a state of rapid development today, and will remain so for the forseeable future. Nevertheless, in the context of this conference it is worth emphasizing that in the diagnostic problem radiation plays an essentially passive role; it is merely the tool used to analyze the situation.

Accurate Radiation Hydrodynamics and MHD Modeling of 3-D Stellar Atmospheres

2009 ◽  
Author(s):  
Å. Nordlund ◽  
R. F. Stein ◽  
Ivan Hubeny ◽  
James M. Stone ◽  
Keith MacGregor ◽  
...  
Keyword(s):  
Stellar Atmospheres ◽  
Radiation Hydrodynamics ◽  
Mhd Modeling

Some Problems in Understanding the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 1-9
Author(s):  
A. H. Gabriel
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Theoretical Modelling ◽  
Total System ◽  
Major Advance ◽  
X Ray ◽  
Proper Perspective ◽  
Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

Influence of Magnetic Fields on Solar Hydrodynamics: Experimental Results

1977 ◽  
Vol 36 ◽  
pp. 143-180 ◽  
Author(s):  
J.O. Stenflo
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
General Problem ◽  
Solar Rotation ◽  
Active Regions ◽  
Physical Conditions ◽  
Dynamic Phenomena

It is well-known that solar activity is basically caused by the Interaction of magnetic fields with convection and solar rotation, resulting in a great variety of dynamic phenomena, like flares, surges, sunspots, prominences, etc. Many conferences have been devoted to solar activity, including the role of magnetic fields. Similar attention has not been paid to the role of magnetic fields for the overall dynamics and energy balance of the solar atmosphere, related to the general problem of chromospheric and coronal heating. To penetrate this problem we have to focus our attention more on the physical conditions in the ‘quiet’ regions than on the conspicuous phenomena in active regions.

Gold liposomes

1996 ◽  
Vol 54 ◽  
pp. 898-899
Author(s):  
James F. Hainfeld
Keyword(s):  
Direct Methods ◽  
Important Class ◽  
Double Bonds ◽  
Membrane Phospholipids ◽  
Essential Ingredient ◽  
Lipid Structures

Lipids are an important class of molecules, being found in membranes, HDL, LDL, and other natural structures, serving essential roles in structure and with varied functions such as compartmentalization and transport. Synthetic liposomes are also widely used as delivery and release vehicles for drugs, cosmetics, and other chemicals; soap is made from lipids. Lipids may form bilayer or multilammellar vesicles, micelles, sheets, tubes, and other structures. Lipid molecules may be linked to proteins, carbohydrates, or other moieties. EM study of this essential ingredient of life has lagged, due to lack of direct methods to visualize lipids without extensive alteration. OsO4 reacts with double bonds in membrane phospholipids, forming crossbridges. This has been the method of choice to both fix and stain membranes, thus far. An earlier work described the use of tungstate clusters (W11) attached to lipid moieties to form lipid structures and lipid probes.

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