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H K Biernat - One of the best experts on this subject based on the ideXlab platform.
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Kelvin-Helmholtz Instability and vortices around unmagnetized planets: A numerical simulation
2010Co-Authors: U.v. Amerstorfer, N. V. Erkaev, U. Taubenschuss, H K BiernatAbstract:Results of 2D nonlinear numerical simulations of the magnetohydrodynamic Kelvin-Helmholtz Instability are presented. We assume a boundary layer of a certain width, which separates the plasma in the upper from the plasma in the lower layer. Such a configuration is similar to the situation around unmagnetized planets, where the solar wind (upper plasma layer) streams along the ionosphere (lower plasma layer). At unmagnetized planets, the mass density increases toward the planet. We investigate the influence of a density increase toward the planet on the development and evolution of the Kelvin-Helmholtz Instability and vortices.
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on Kelvin Helmholtz Instability due to the solar wind interaction with unmagnetized planets
Planetary and Space Science, 2007Co-Authors: U.v. Amerstorfer, H K Biernat, N. V. Erkaev, D. LangmayrAbstract:Abstract In this paper, the Kelvin–Helmholtz Instability is studied by solving the ideal MHD equations for a compressible plasma. A transition layer of finite thickness between two plasmas, across which the magnitude of the velocity and the density change, is assumed. Growth rates are presented for the transverse case, i.e., the flow velocity is perpendicular to the magnetic field. If only the velocity changes across the boundary layer and the density is kept constant, an important quantity affecting the growth of the Kelvin–Helmholtz Instability is the magnetosonic Mach number, which characterizes compressibility. The growth rates for the case when both, the velocity and the density, change are very sensitive to the ratio of the upper plasma density to the lower plasma density: a decrease of the density ratio yields a decrease of the growth rate. Including a density profile is very important for the application of the Kelvin–Helmholtz Instability to the solar wind flow around unmagnetized planets, e.g., Venus, where the plasma density increases from the magnetosheath to the ionosphere.
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ion loss on mars caused by the Kelvin Helmholtz Instability
Planetary and Space Science, 2004Co-Authors: T. Penz, Nikolai V. Erkaev, U.v. Amerstorfer, Herbert Gunell, H K Biernat, H Lammer, Esa KallioAbstract:Abstract Mars Global Surveyor detected cold electrons above the Martian ionopause, which can be interpreted as detached ionospheric plasma clouds. Similar observations by the Pioneer Venus Orbiter electron temperature probe showed also extreme spatial irregularities of electrons in the form of plasma clouds on Venus, which were explained by the occurrence of the Kelvin–Helmholtz Instability. Therefore, we suggest that the Kelvin–Helmholtz Instability may also detach ionospheric plasma clouds on Mars. We investigate the Instability growth rate at the Martian ionopause resulting from the flow of the solar wind for the case where the interplanetary magnetic field is oriented normal to the flow direction. Since the velocity shear near the subsolar point is very small, this area is stable with respect to the Kelvin–Helmholtz Instability. We found that the highest flow velocities are reached at the equatorial flanks near the terminator plane, while the maximum plasma density in the terminator plane appears at the polar areas. By comparing the Instability growth rate with the magnetic barrier formation time, we found that the Instability can evolve into a non-linear stage at the whole terminator plane but preferably at the equatorial flanks. Escape rates of O + ions due to detached plasma clouds in the order of about 2 × 10 23 – 3 × 10 24 s - 1 are found. Thus, atmospheric loss caused by the Kelvin–Helmholtz Instability should be comparable with other non-thermal loss processes. Further, we discuss our results in view of the expected observations of heavy ion loss rates by ASPERA-3 on board of Mars Express.
U.v. Amerstorfer - One of the best experts on this subject based on the ideXlab platform.
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Kelvin-Helmholtz Instability and vortices around unmagnetized planets: A numerical simulation
2010Co-Authors: U.v. Amerstorfer, N. V. Erkaev, U. Taubenschuss, H K BiernatAbstract:Results of 2D nonlinear numerical simulations of the magnetohydrodynamic Kelvin-Helmholtz Instability are presented. We assume a boundary layer of a certain width, which separates the plasma in the upper from the plasma in the lower layer. Such a configuration is similar to the situation around unmagnetized planets, where the solar wind (upper plasma layer) streams along the ionosphere (lower plasma layer). At unmagnetized planets, the mass density increases toward the planet. We investigate the influence of a density increase toward the planet on the development and evolution of the Kelvin-Helmholtz Instability and vortices.
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on Kelvin Helmholtz Instability due to the solar wind interaction with unmagnetized planets
Planetary and Space Science, 2007Co-Authors: U.v. Amerstorfer, H K Biernat, N. V. Erkaev, D. LangmayrAbstract:Abstract In this paper, the Kelvin–Helmholtz Instability is studied by solving the ideal MHD equations for a compressible plasma. A transition layer of finite thickness between two plasmas, across which the magnitude of the velocity and the density change, is assumed. Growth rates are presented for the transverse case, i.e., the flow velocity is perpendicular to the magnetic field. If only the velocity changes across the boundary layer and the density is kept constant, an important quantity affecting the growth of the Kelvin–Helmholtz Instability is the magnetosonic Mach number, which characterizes compressibility. The growth rates for the case when both, the velocity and the density, change are very sensitive to the ratio of the upper plasma density to the lower plasma density: a decrease of the density ratio yields a decrease of the growth rate. Including a density profile is very important for the application of the Kelvin–Helmholtz Instability to the solar wind flow around unmagnetized planets, e.g., Venus, where the plasma density increases from the magnetosheath to the ionosphere.
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On Kelvin–Helmholtz Instability due to the solar wind interaction with unmagnetized planets
Planetary and Space Science, 2007Co-Authors: U.v. Amerstorfer, Nikolai V. Erkaev, D. Langmayr, Helfried K. BiernatAbstract:Abstract In this paper, the Kelvin–Helmholtz Instability is studied by solving the ideal MHD equations for a compressible plasma. A transition layer of finite thickness between two plasmas, across which the magnitude of the velocity and the density change, is assumed. Growth rates are presented for the transverse case, i.e., the flow velocity is perpendicular to the magnetic field. If only the velocity changes across the boundary layer and the density is kept constant, an important quantity affecting the growth of the Kelvin–Helmholtz Instability is the magnetosonic Mach number, which characterizes compressibility. The growth rates for the case when both, the velocity and the density, change are very sensitive to the ratio of the upper plasma density to the lower plasma density: a decrease of the density ratio yields a decrease of the growth rate. Including a density profile is very important for the application of the Kelvin–Helmholtz Instability to the solar wind flow around unmagnetized planets, e.g., Venus, where the plasma density increases from the magnetosheath to the ionosphere.
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ion loss on mars caused by the Kelvin Helmholtz Instability
Planetary and Space Science, 2004Co-Authors: T. Penz, Nikolai V. Erkaev, U.v. Amerstorfer, Herbert Gunell, H K Biernat, H Lammer, Esa KallioAbstract:Abstract Mars Global Surveyor detected cold electrons above the Martian ionopause, which can be interpreted as detached ionospheric plasma clouds. Similar observations by the Pioneer Venus Orbiter electron temperature probe showed also extreme spatial irregularities of electrons in the form of plasma clouds on Venus, which were explained by the occurrence of the Kelvin–Helmholtz Instability. Therefore, we suggest that the Kelvin–Helmholtz Instability may also detach ionospheric plasma clouds on Mars. We investigate the Instability growth rate at the Martian ionopause resulting from the flow of the solar wind for the case where the interplanetary magnetic field is oriented normal to the flow direction. Since the velocity shear near the subsolar point is very small, this area is stable with respect to the Kelvin–Helmholtz Instability. We found that the highest flow velocities are reached at the equatorial flanks near the terminator plane, while the maximum plasma density in the terminator plane appears at the polar areas. By comparing the Instability growth rate with the magnetic barrier formation time, we found that the Instability can evolve into a non-linear stage at the whole terminator plane but preferably at the equatorial flanks. Escape rates of O + ions due to detached plasma clouds in the order of about 2 × 10 23 – 3 × 10 24 s - 1 are found. Thus, atmospheric loss caused by the Kelvin–Helmholtz Instability should be comparable with other non-thermal loss processes. Further, we discuss our results in view of the expected observations of heavy ion loss rates by ASPERA-3 on board of Mars Express.
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Ion loss on Mars caused by the Kelvin–Helmholtz Instability
Planetary and Space Science, 2004Co-Authors: T. Penz, Helmut Lammer, Helfried K. Biernat, Nikolai V. Erkaev, U.v. Amerstorfer, Herbert Gunell, Esa Kallio, S. Barabash, Stefano Orsini, A. MililloAbstract:Abstract Mars Global Surveyor detected cold electrons above the Martian ionopause, which can be interpreted as detached ionospheric plasma clouds. Similar observations by the Pioneer Venus Orbiter electron temperature probe showed also extreme spatial irregularities of electrons in the form of plasma clouds on Venus, which were explained by the occurrence of the Kelvin–Helmholtz Instability. Therefore, we suggest that the Kelvin–Helmholtz Instability may also detach ionospheric plasma clouds on Mars. We investigate the Instability growth rate at the Martian ionopause resulting from the flow of the solar wind for the case where the interplanetary magnetic field is oriented normal to the flow direction. Since the velocity shear near the subsolar point is very small, this area is stable with respect to the Kelvin–Helmholtz Instability. We found that the highest flow velocities are reached at the equatorial flanks near the terminator plane, while the maximum plasma density in the terminator plane appears at the polar areas. By comparing the Instability growth rate with the magnetic barrier formation time, we found that the Instability can evolve into a non-linear stage at the whole terminator plane but preferably at the equatorial flanks. Escape rates of O + ions due to detached plasma clouds in the order of about 2 × 10 23 – 3 × 10 24 s - 1 are found. Thus, atmospheric loss caused by the Kelvin–Helmholtz Instability should be comparable with other non-thermal loss processes. Further, we discuss our results in view of the expected observations of heavy ion loss rates by ASPERA-3 on board of Mars Express.
J. B. Thoo - One of the best experts on this subject based on the ideXlab platform.
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ON THE WEAKLY NONLINEAR Kelvin-Helmholtz Instability OF TANGENTIAL DISCONTINUITIES IN MHD
Journal of Hyperbolic Differential Equations, 2011Co-Authors: John K. Hunter, J. B. ThooAbstract:We derive a quadratically nonlinear equation that describes the motion of a tangential discontinuity in incompressible magnetohydrodynamics near the onset of a Kelvin–Helmholtz Instability. We show that nonlinear effects enhance the Instability and give a criterion for it to occur in terms of a longitudinal strain of the fluid motion along the discontinuity.
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ON THE WEAKLY NONLINEAR Kelvin–Helmholtz Instability OF TANGENTIAL DISCONTINUITIES IN MHD
Journal of Hyperbolic Differential Equations, 2011Co-Authors: John K. Hunter, J. B. ThooAbstract:We derive a quadratically nonlinear equation that describes the motion of a tangential discontinuity in incompressible magnetohydrodynamics near the onset of a Kelvin–Helmholtz Instability. We show that nonlinear effects enhance the Instability and give a criterion for it to occur in terms of a longitudinal strain of the fluid motion along the discontinuity.
F. Pegoraro - One of the best experts on this subject based on the ideXlab platform.
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magnetised Kelvin Helmholtz Instability in the intermediate regime between subsonic and supersonic regimes
Physics of Plasmas, 2012Co-Authors: Pierre Henri, M. Faganello, Francesco Califano, F. PegoraroAbstract:The understanding of the dynamics at play at the Earth’s Magnetopause, the boundary separating the Earth’s magnetosphere and the solar wind plasmas, is of primary importance for space plasma modeling. We focus our attention on the low latitude flank of the magnetosphere where the velocity shear between the magnetosheath and the magnetospheric plasmas is the energetic source of Kelvin-Helmholtz Instability. On the shoulder of the resulting vortex chain, different secondary instabilities are at play depending on the local plasma parameters and compete with the vortex pairing process. Most important, secondary instabilities, among other magnetic reconnection, control the plasma mixing as well as the entry of solar wind plasma in the magnetosphere. We make use of a two-fluid model, including the Hall term and the electron mass in the generalized Ohm’s law, to study the 2D non-linear evolution of the Kelvin-Helmholtz Instability at the magnetosheath–magnetosphere interface, in the intermediate regime between s...
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Compressible Kelvin-Helmholtz Instability in supermagnetosonic regimes
Journal of Geophysical Research Space Physics, 2011Co-Authors: F. Palermo, M. Faganello, F. Califano, F. Pegoraro, Olivier Le ContelAbstract:We investigate the transition from submagnetosonic to supermagnetosonic regimes in the presence of a sheared flow and density variations typically observed between the solar wind and the Earth's magnetosphere. In particular, we show the possibility of generating quasi-perpendicular magnetosonic shock structures under typical conditions that can be realized at the magnetosphere flanks. Here the Kelvin-Helmholtz Instability generates rolled-up, large- scale vortices that propagate along the flanks of the magnetosphere. The shocks are generated by those vortices for which the magnetosonic Mach number turns out to be of the order of unity or larger.
S. E. Korshunov - One of the best experts on this subject based on the ideXlab platform.
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Analog of Kelvin-Helmholtz Instability on superfluid liquid free surface
arXiv: Condensed Matter, 2002Co-Authors: S. E. KorshunovAbstract:We analyse the analog of the Kelvin-Helmholtz Instability on free suface of a superfluid liquid. This Instability is induced by the relative motion of superfluid and normal components of the same liquid along the surface. The Instability threshold is found to be independent of the value of viscosity, but turns out to be lower than in absence of dissipation. The result is similar to that obtained for the interface between two sliding superfluids (with different mechanism of dissipation) and confirmed by the first experimental observation of the Kelvin-Helmholtz Instability on the interface between A and B phases of superfluid helium-3 by Blaauwgeers et al. (cond-mat/0111343).
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Analog of Kelvin-Helmholtz Instability on a free surface of a superfluid liquid
Journal of Experimental and Theoretical Physics Letters, 2002Co-Authors: S. E. KorshunovAbstract:We analyze the analog of the Kelvin-Helmholtz Instability on the free surface of a superfluid liquid. This Instability is induced by the relative motion of superfluid and normal components of the same liquid along the surface. The Instability threshold is found to be independent of the value of viscosity, but turns out to be lower than in the absence of dissipation. The result is similar to that obtained for the interface between two sliding super-fluids (with different mechanisms of dissipation) and confirmed by the first experimental observation of the Kelvin-Helmholtz Instability on the interface between 3He-A and 3He-B by Blaauwgeers et al. (cond-mat/0111343).
