Supersonic mixing layers: Stability of magnetospheric flanks models

Compressibility has a strong influence on the stability of velocity shear layers when the difference of velocity ΔV across the flow becomes supersonic. The flanks of the Earth's magnetopause are normally supersonic Ms > 1, and super-Alfvénic MA > 1, depending on the distance from...

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Autores principales: Gnavi, Graciela Delia, Gratton, Fausto Tulio Livio, Bilbao, Luis Ernesto
Publicado: 2009
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_17426588_v166_n_p_Gnavi
http://hdl.handle.net/20.500.12110/paper_17426588_v166_n_p_Gnavi
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_17426588_v166_n_p_Gnavi2023-06-08T16:27:11Z Supersonic mixing layers: Stability of magnetospheric flanks models Gnavi, Graciela Delia Gratton, Fausto Tulio Livio Bilbao, Luis Ernesto Compressibility has a strong influence on the stability of velocity shear layers when the difference of velocity ΔV across the flow becomes supersonic. The flanks of the Earth's magnetopause are normally supersonic Ms > 1, and super-Alfvénic MA > 1, depending on the distance from the dayside terminator (Ms and MA are the sonic and Alfvén Mach numbers of the magnetosheath plasma, respectively). The stability of MHD supersonic flows depends, also on several other features, such as the finite thickness Δ of the boundary layer, the relative orientation of velocity and magnetic fields, the density jump across the boundary and the magnetic shear angle. We analyze the MHD stability of some representative flank sites modeled after data from spacecraft crossings of the magnetopause under different interplanetary conditions, complementing these cases with extrapolations of likely conditions upstream, and downstream of the crossing site. Under northward interplanetary magnetic field conditions, there are solar wind regimes such that the near, but already supersonic, flank of the magnetopause may be locally stable. Stability is possible, e.g., when M s becomes larger than ∼1.2-1.4 while MA remains smaller than 1.2, and there is magnetic shear between the geomagnetic and the interplanetary magnetic field. Solar winds favouring local stability of the boundary layer are cold, not-too-dense plasmas, with strong magnetic fields, so that MA is smaller, while Ms is larger, than normal values of the magnetosheath flow. A gap between dayside and tail amplifying regions of Kelvin-Helmholtz disturbances over the magnetopause may exist when the above conditions are realized. © 2009 IOP Publishing Ltd. Fil:Gnavi, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Gratton, F.T. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Bilbao, L.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2009 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_17426588_v166_n_p_Gnavi http://hdl.handle.net/20.500.12110/paper_17426588_v166_n_p_Gnavi
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description Compressibility has a strong influence on the stability of velocity shear layers when the difference of velocity ΔV across the flow becomes supersonic. The flanks of the Earth's magnetopause are normally supersonic Ms > 1, and super-Alfvénic MA > 1, depending on the distance from the dayside terminator (Ms and MA are the sonic and Alfvén Mach numbers of the magnetosheath plasma, respectively). The stability of MHD supersonic flows depends, also on several other features, such as the finite thickness Δ of the boundary layer, the relative orientation of velocity and magnetic fields, the density jump across the boundary and the magnetic shear angle. We analyze the MHD stability of some representative flank sites modeled after data from spacecraft crossings of the magnetopause under different interplanetary conditions, complementing these cases with extrapolations of likely conditions upstream, and downstream of the crossing site. Under northward interplanetary magnetic field conditions, there are solar wind regimes such that the near, but already supersonic, flank of the magnetopause may be locally stable. Stability is possible, e.g., when M s becomes larger than ∼1.2-1.4 while MA remains smaller than 1.2, and there is magnetic shear between the geomagnetic and the interplanetary magnetic field. Solar winds favouring local stability of the boundary layer are cold, not-too-dense plasmas, with strong magnetic fields, so that MA is smaller, while Ms is larger, than normal values of the magnetosheath flow. A gap between dayside and tail amplifying regions of Kelvin-Helmholtz disturbances over the magnetopause may exist when the above conditions are realized. © 2009 IOP Publishing Ltd.
author Gnavi, Graciela Delia
Gratton, Fausto Tulio Livio
Bilbao, Luis Ernesto
spellingShingle Gnavi, Graciela Delia
Gratton, Fausto Tulio Livio
Bilbao, Luis Ernesto
Supersonic mixing layers: Stability of magnetospheric flanks models
author_facet Gnavi, Graciela Delia
Gratton, Fausto Tulio Livio
Bilbao, Luis Ernesto
author_sort Gnavi, Graciela Delia
title Supersonic mixing layers: Stability of magnetospheric flanks models
title_short Supersonic mixing layers: Stability of magnetospheric flanks models
title_full Supersonic mixing layers: Stability of magnetospheric flanks models
title_fullStr Supersonic mixing layers: Stability of magnetospheric flanks models
title_full_unstemmed Supersonic mixing layers: Stability of magnetospheric flanks models
title_sort supersonic mixing layers: stability of magnetospheric flanks models
publishDate 2009
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_17426588_v166_n_p_Gnavi
http://hdl.handle.net/20.500.12110/paper_17426588_v166_n_p_Gnavi
work_keys_str_mv AT gnavigracieladelia supersonicmixinglayersstabilityofmagnetosphericflanksmodels
AT grattonfaustotuliolivio supersonicmixinglayersstabilityofmagnetosphericflanksmodels
AT bilbaoluisernesto supersonicmixinglayersstabilityofmagnetosphericflanksmodels
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