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I C F Mullerwodarg - One of the best experts on this subject based on the ideXlab platform.
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on the global distribution of Neutral Gases in titan s upper atmosphere and its effect on the thermal structure
Journal of Geophysical Research, 2003Co-Authors: R V Yelle, I C F Mullerwodarg, Michael Mendillo, A D AylwardAbstract:[1] Using a time-dependent general circulation model of Titan’s thermosphere, we calculate the global distribution of Neutral Gases by winds and diffusion. Our calculations suggest that solar driven dynamics effectively redistribute constituents, causing considerable diurnal and seasonal changes in gas abundances. Subsidence causes an accumulation of lighter Gases on the nightside, with nighttime CH4 mole fractions at equinox near 1400 km reaching up to 50%. The reverse happens on the dayside, where lighter Gases are depleted, giving minimum CH4 mole fractions near 1400 km of around 12%. The vertical transport time scales are around 5–10% of a Titan day, so these extrema in gas abundances are shifted with respect to local noon and midnight by up to 4 hours Local Solar Time (LST). The strong horizontal variations in gas abundances, combined with the local time shifts of their extrema, have an important impact on the thermal structure and lead to a shift of the nighttime minimum from local midnight towards early morning hours (0330 LST). This coupling between gas distribution and thermal structure on the nightside occurs via dynamical processes, primarily through changes in adiabatic heating. The redistribution of Gases effectively controls, through changes in mean molecular weight, the pressure gradients, which in turn control the horizontal and vertical winds, and thereby adiabatic heating and cooling. On the dayside, changes in solar EUV absorption due to the redistributed Gases occur but are comparatively small. Although it is possible with our calculations to identify important processes, Voyager and ground based observations of Titan are currently not sufficient to constrain the dynamics of Titan’s upper atmosphere, but comparisons with forthcoming Cassini observations are highly anticipated. INDEX TERMS: 6005 Planetology: Comets and Small Bodies: Atmospheres—composition and chemistry; 0355 Atmospheric Composition and Structure: Thermosphere—composition and chemistry; 3210 Mathematical Geophysics: Modeling; 6007 Planetology: Comets and Small Bodies: Atmospheres—structure and dynamics; 6025 Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields;
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on the global distribution of Neutral Gases in titan s upper atmosphere and its effect on the thermal structure
Journal of Geophysical Research, 2003Co-Authors: R V Yelle, I C F Mullerwodarg, Michael Mendillo, A D AylwardAbstract:[1] Using a time-dependent general circulation model of Titan’s thermosphere, we calculate the global distribution of Neutral Gases by winds and diffusion. Our calculations suggest that solar driven dynamics effectively redistribute constituents, causing considerable diurnal and seasonal changes in gas abundances. Subsidence causes an accumulation of lighter Gases on the nightside, with nighttime CH4 mole fractions at equinox near 1400 km reaching up to 50%. The reverse happens on the dayside, where lighter Gases are depleted, giving minimum CH4 mole fractions near 1400 km of around 12%. The vertical transport time scales are around 5–10% of a Titan day, so these extrema in gas abundances are shifted with respect to local noon and midnight by up to 4 hours Local Solar Time (LST). The strong horizontal variations in gas abundances, combined with the local time shifts of their extrema, have an important impact on the thermal structure and lead to a shift of the nighttime minimum from local midnight towards early morning hours (0330 LST). This coupling between gas distribution and thermal structure on the nightside occurs via dynamical processes, primarily through changes in adiabatic heating. The redistribution of Gases effectively controls, through changes in mean molecular weight, the pressure gradients, which in turn control the horizontal and vertical winds, and thereby adiabatic heating and cooling. On the dayside, changes in solar EUV absorption due to the redistributed Gases occur but are comparatively small. Although it is possible with our calculations to identify important processes, Voyager and ground based observations of Titan are currently not sufficient to constrain the dynamics of Titan’s upper atmosphere, but comparisons with forthcoming Cassini observations are highly anticipated. INDEX TERMS: 6005 Planetology: Comets and Small Bodies: Atmospheres—composition and chemistry; 0355 Atmospheric Composition and Structure: Thermosphere—composition and chemistry; 3210 Mathematical Geophysics: Modeling; 6007 Planetology: Comets and Small Bodies: Atmospheres—structure and dynamics; 6025 Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields;
Håkan Andréasson - One of the best experts on this subject based on the ideXlab platform.
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The Einstein–Vlasov System/Kinetic Theory
2014Co-Authors: Håkan AndréassonAbstract:The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein–Vlasov system. This system couples Einstein’s equations to a kinetic matter model. Kinetic theory has been an important field of research during several decades in which the main focus has been on nonrelativistic and special rela-tivistic physics, i.e. to model the dynamics of Neutral Gases, plasmas, and Newtonian self-gravitating systems. In 1990, Rendall and Rein initiated a mathematical study of the Einstein–Vlasov system. Since then many theorems on global properties of solutions to this system have been established. The Vlasov equation describes matter phe-nomenologically, and it should be stressed that most of the theorems presented in this article are not presently known for other such matter models (i.e. fluid models). This paper gives introductions to kinetic theory in non-curved spacetimes and then the Einstein–Vlasov syste
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the einstein vlasov system kinetic theory
arXiv: General Relativity and Quantum Cosmology, 2011Co-Authors: Håkan AndréassonAbstract:The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein--Vlasov system. This system couples Einstein's equations to a kinetic matter model. Kinetic theory has been an important field of research during several decades in which the main focus has been on non-relativistic and special relativistic physics, i.e., to model the dynamics of Neutral Gases, plasmas, and Newtonian self-gravitating systems. In 1990, Rendall and Rein initiated a mathematical study of the Einstein--Vlasov system. Since then many theorems on global properties of solutions to this system have been established.
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The Einstein-Vlasov System/Kinetic Theory
Living Reviews in Relativity, 2011Co-Authors: Håkan AndréassonAbstract:The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein-Vlasov system. This system couples Einstein’s equations to a kinetic matter model. Kinetic theory has been an important field of research during several decades in which the main focus has been on non-relativistic and special relativistic physics, i.e., to model the dynamics of Neutral Gases, plasmas, and Newtonian self-gravitating systems. In 1990, Rendall and Rein initiated a mathematical study of the Einstein-Vlasov system. Since then many theorems on global properties of solutions to this system have been established. This paper gives introductions to kinetic theory in non-curved spacetimes and then the Einstein-Vlasov system is introduced. We believe that a good understanding of kinetic theory in non-curved spacetimes is fundamental to a good comprehension of kinetic theory in general relativity.
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the einstein vlasov system kinetic theory
Living Reviews in Relativity, 2002Co-Authors: Håkan AndréassonAbstract:The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein-Vlasov system. This system couples Einstein’s equations to a kinetic matter model. Kinetic theory has been an important field of research during several decades in which the main focus has been on nonrelativistic and special relativistic physics, i.e. to model the dynamics of Neutral Gases, plasmas, and Newtonian self-gravitating systems. In 1990, Rendall and Rein initiated a mathematical study of the Einstein-Vlasov system. Since then many theorems on global properties of solutions to this system have been established. The Vlasov equation describes matter phenomenologically, and it should be stressed that most of the theorems presented in this article are not presently known for other such matter models (i.e. fluid models). This paper gives introductions to kinetic theory in non-curved spacetimes and then the Einstein-Vlasov system is introduced. We believe that a good understanding of kinetic theory in non-curved spacetimes is fundamental to good comprehension of kinetic theory in general relativity.
Daniel Zimmer - One of the best experts on this subject based on the ideXlab platform.
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laser driven parametric amplification of xuv and soft x rays in Neutral Gases
International Conference on Ultrafast Phenomena (2010) paper TuA5, 2010Co-Authors: J Seres, E Seres, Daniel Hochhaus, Boris Ecker, Daniel Zimmer, V Bagnoud, B Aurand, B Zielbauer, T Kuehl, Christian SpielmannAbstract:We present the first theoretical description and also experimental evidence for the amplification of XUV and soft-X-ray radiation by parametric stimulated emission in Neutral Gases driven by near-IR laser pulses reaching small-signal-gain up to 8000.
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laser driven amplification of soft x rays by parametric stimulated emission in Neutral Gases
Nature Physics, 2010Co-Authors: J Seres, E Seres, Daniel Hochhaus, Boris Ecker, Daniel ZimmerAbstract:The high-order harmonics of short laser pulses created in a nonlinear medium are a useful source of extreme-ultraviolet and soft-X-ray radiation. A newly discovered phenomenon that amplifies this emission even further could improve the efficiency of short-wavelength light sources.
A. V. Pavlov - One of the best experts on this subject based on the ideXlab platform.
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thermodiffusion and diffusion correction factors of Neutral Gases in the earth s atmosphere
Surveys in Geophysics, 2021Co-Authors: A. V. PavlovAbstract:The Maxwell–Stefan diffusion equations for multicomponent Neutral gas mixtures with thermodiffusion ratios and diffusion correction factors in the Chapman–Cowling third-order approximation are derived. These thermodiffusion ratios and diffusion correction factors are presented explicitly as functions of masses, number densities, thermal conductivities, and the Chapman–Cowling collision integrals of the Neutral species under consideration. Applications to the multicomponent mixture of atmospheric Neutral Gases O, N2, O2, He, H, Ar, H2, N, and NO are considered, and recommendations are given for using the results of this paper in studies of the Earth's atmosphere.
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correction to diffusion and thermodiffusion of atmospheric Neutral Gases a review
Surveys in Geophysics, 2020Co-Authors: A. V. PavlovAbstract:The original version of this article unfortunately contained misprints. The corrections of these misprints are given below.
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Diffusion and Thermodiffusion of Atmospheric Neutral Gases: A Review
Surveys in Geophysics, 2019Co-Authors: A. V. PavlovAbstract:The current state of knowledge on diffusion and thermodiffusion of Neutral Gases that govern the composition of the greater part of the Earth’s thermosphere is reviewed. Hydrodynamic equations determining diffusion velocities of Neutral Gases of the multicomponent atmosphere are considered in the first-order approximation of the velocity distribution functions of the Chapman–Enskog method using the first- and second-order approximations of the Sonine polynomial expansion to transport multicomponent coefficients of Neutral Gases. The interrelations among various definitions for the multicomponent diffusivities are given. The thermodiffusion factors and binary diffusion coefficients of N_2, O_2, O, He, H, Ar, N, NO, and H_2 used in atmospheric studies to calculate the diffusion velocities and number densities of these atmospheric Gases are discussed. The recommended temperature dependencies of the binary diffusion coefficients and the recommended average multicomponent diffusion correction and thermodiffusion factors of the atmospheric Neutral Gases under consideration are presented.
A D Aylward - One of the best experts on this subject based on the ideXlab platform.
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on the global distribution of Neutral Gases in titan s upper atmosphere and its effect on the thermal structure
Journal of Geophysical Research, 2003Co-Authors: R V Yelle, I C F Mullerwodarg, Michael Mendillo, A D AylwardAbstract:[1] Using a time-dependent general circulation model of Titan’s thermosphere, we calculate the global distribution of Neutral Gases by winds and diffusion. Our calculations suggest that solar driven dynamics effectively redistribute constituents, causing considerable diurnal and seasonal changes in gas abundances. Subsidence causes an accumulation of lighter Gases on the nightside, with nighttime CH4 mole fractions at equinox near 1400 km reaching up to 50%. The reverse happens on the dayside, where lighter Gases are depleted, giving minimum CH4 mole fractions near 1400 km of around 12%. The vertical transport time scales are around 5–10% of a Titan day, so these extrema in gas abundances are shifted with respect to local noon and midnight by up to 4 hours Local Solar Time (LST). The strong horizontal variations in gas abundances, combined with the local time shifts of their extrema, have an important impact on the thermal structure and lead to a shift of the nighttime minimum from local midnight towards early morning hours (0330 LST). This coupling between gas distribution and thermal structure on the nightside occurs via dynamical processes, primarily through changes in adiabatic heating. The redistribution of Gases effectively controls, through changes in mean molecular weight, the pressure gradients, which in turn control the horizontal and vertical winds, and thereby adiabatic heating and cooling. On the dayside, changes in solar EUV absorption due to the redistributed Gases occur but are comparatively small. Although it is possible with our calculations to identify important processes, Voyager and ground based observations of Titan are currently not sufficient to constrain the dynamics of Titan’s upper atmosphere, but comparisons with forthcoming Cassini observations are highly anticipated. INDEX TERMS: 6005 Planetology: Comets and Small Bodies: Atmospheres—composition and chemistry; 0355 Atmospheric Composition and Structure: Thermosphere—composition and chemistry; 3210 Mathematical Geophysics: Modeling; 6007 Planetology: Comets and Small Bodies: Atmospheres—structure and dynamics; 6025 Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields;
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on the global distribution of Neutral Gases in titan s upper atmosphere and its effect on the thermal structure
Journal of Geophysical Research, 2003Co-Authors: R V Yelle, I C F Mullerwodarg, Michael Mendillo, A D AylwardAbstract:[1] Using a time-dependent general circulation model of Titan’s thermosphere, we calculate the global distribution of Neutral Gases by winds and diffusion. Our calculations suggest that solar driven dynamics effectively redistribute constituents, causing considerable diurnal and seasonal changes in gas abundances. Subsidence causes an accumulation of lighter Gases on the nightside, with nighttime CH4 mole fractions at equinox near 1400 km reaching up to 50%. The reverse happens on the dayside, where lighter Gases are depleted, giving minimum CH4 mole fractions near 1400 km of around 12%. The vertical transport time scales are around 5–10% of a Titan day, so these extrema in gas abundances are shifted with respect to local noon and midnight by up to 4 hours Local Solar Time (LST). The strong horizontal variations in gas abundances, combined with the local time shifts of their extrema, have an important impact on the thermal structure and lead to a shift of the nighttime minimum from local midnight towards early morning hours (0330 LST). This coupling between gas distribution and thermal structure on the nightside occurs via dynamical processes, primarily through changes in adiabatic heating. The redistribution of Gases effectively controls, through changes in mean molecular weight, the pressure gradients, which in turn control the horizontal and vertical winds, and thereby adiabatic heating and cooling. On the dayside, changes in solar EUV absorption due to the redistributed Gases occur but are comparatively small. Although it is possible with our calculations to identify important processes, Voyager and ground based observations of Titan are currently not sufficient to constrain the dynamics of Titan’s upper atmosphere, but comparisons with forthcoming Cassini observations are highly anticipated. INDEX TERMS: 6005 Planetology: Comets and Small Bodies: Atmospheres—composition and chemistry; 0355 Atmospheric Composition and Structure: Thermosphere—composition and chemistry; 3210 Mathematical Geophysics: Modeling; 6007 Planetology: Comets and Small Bodies: Atmospheres—structure and dynamics; 6025 Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields;