The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma

The hydromagnetic Kelvin-Helmholtz instability is relevant in many complex situations in astrophysical and laboratory plasmas. Many cases of interest are very complicated, since they involve the combined role of velocity shear, of density and magnetic field stratification, and of various geometries...

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Detalles Bibliográficos
Autores principales: González, Alejandro Guillermo, Gratton, Julio
Publicado: 1994
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00223778_v52_n2_p223_Gonzalez
http://hdl.handle.net/20.500.12110/paper_00223778_v52_n2_p223_Gonzalez
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_00223778_v52_n2_p223_Gonzalez
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spelling paper:paper_00223778_v52_n2_p223_Gonzalez2023-06-08T14:50:30Z The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma González, Alejandro Guillermo Gratton, Julio The hydromagnetic Kelvin-Helmholtz instability is relevant in many complex situations in astrophysical and laboratory plasmas. Many cases of interest are very complicated, since they involve the combined role of velocity shear, of density and magnetic field stratification, and of various geometries in compressible plasmas. In the present work we continue investigating the influence of various physical and geometrical parameters of the plasma on the Kelvin-Helmholtz modes. We use the general dispersion relation for the ideal compressible MHD modes localized near a velocity discontinuity between two uniform plasmas. We study analytically the existence and properties of the modes and their stability, for a velocity jump combined with a density jump, and for any relative orientation of B, u and k (B is continuous). Stability is analysed by means of a general procedure that allows discussion of any configuration and all kinds of perturbations. The boundaries between modes of different kinds are discussed. In contrast to the case of uniform density, for a density jump there are no monotonically unstable modes, only overstabilities. The unstable modes belong to two types. Those with the largest growth rates tend to monotonically unstable modes in the limit of uniform density, and are related to the torsional Alfven mode. The other overstable modes have no analogue among the purely incompressible modes, and occur in a range of U that is stable in the incompressible limit. We derive bounds for the growth rate of the instability. The present results may serve as a guide to interpret results in more complicated and realistic situations as those occurring in laboratory and natural plasmas. © 1994, Cambridge University Press. All rights reserved. Fil:Gonzalez, A.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Gratton, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 1994 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00223778_v52_n2_p223_Gonzalez http://hdl.handle.net/20.500.12110/paper_00223778_v52_n2_p223_Gonzalez
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description The hydromagnetic Kelvin-Helmholtz instability is relevant in many complex situations in astrophysical and laboratory plasmas. Many cases of interest are very complicated, since they involve the combined role of velocity shear, of density and magnetic field stratification, and of various geometries in compressible plasmas. In the present work we continue investigating the influence of various physical and geometrical parameters of the plasma on the Kelvin-Helmholtz modes. We use the general dispersion relation for the ideal compressible MHD modes localized near a velocity discontinuity between two uniform plasmas. We study analytically the existence and properties of the modes and their stability, for a velocity jump combined with a density jump, and for any relative orientation of B, u and k (B is continuous). Stability is analysed by means of a general procedure that allows discussion of any configuration and all kinds of perturbations. The boundaries between modes of different kinds are discussed. In contrast to the case of uniform density, for a density jump there are no monotonically unstable modes, only overstabilities. The unstable modes belong to two types. Those with the largest growth rates tend to monotonically unstable modes in the limit of uniform density, and are related to the torsional Alfven mode. The other overstable modes have no analogue among the purely incompressible modes, and occur in a range of U that is stable in the incompressible limit. We derive bounds for the growth rate of the instability. The present results may serve as a guide to interpret results in more complicated and realistic situations as those occurring in laboratory and natural plasmas. © 1994, Cambridge University Press. All rights reserved.
author González, Alejandro Guillermo
Gratton, Julio
spellingShingle González, Alejandro Guillermo
Gratton, Julio
The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma
author_facet González, Alejandro Guillermo
Gratton, Julio
author_sort González, Alejandro Guillermo
title The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma
title_short The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma
title_full The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma
title_fullStr The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma
title_full_unstemmed The Role of a Density Jump in the Kelvin-Helmholtz Instability of a Compressible Plasma
title_sort role of a density jump in the kelvin-helmholtz instability of a compressible plasma
publishDate 1994
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00223778_v52_n2_p223_Gonzalez
http://hdl.handle.net/20.500.12110/paper_00223778_v52_n2_p223_Gonzalez
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