Magnetohydrodynamic stellar wind solutions in curved magnetic fields

This paper generalizes the analytic class of magnetohydrodynamic (MHD) solutions introduced by Low and Tsinganos for steady, rotating, axisymmetric stellar winds embedded in partially open magnetic fields. The collimation of the outflow is achieved by assuming a magnetic configuration that not only...

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Autores principales: Rotstein, N.O., Fontán, C.F.
Formato: JOUR
Materias:
MHD
Plasmas
Stars: mass loss
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_0004637X_v449_n2_p745_Rotstein
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_0004637X_v449_n2_p745_Rotstein2023-10-03T14:01:37Z Magnetohydrodynamic stellar wind solutions in curved magnetic fields Rotstein, N.O. Fontán, C.F. MHD Plasmas Stars: mass loss This paper generalizes the analytic class of magnetohydrodynamic (MHD) solutions introduced by Low and Tsinganos for steady, rotating, axisymmetric stellar winds embedded in partially open magnetic fields. The collimation of the outflow is achieved by assuming a magnetic configuration that not only has the property that its field lines are poleward deflected but also includes as particular cases the streamline geometries proposed by other authors. The full MHD equations are reduced to a set of second-order, radial, ordinary differential equations by a suitable choice of the angular dependence of the dynamic and thermodynamic variables. In particular, spherically symmetric Mach-Alfvén surfaces are assumed. The required heating distribution that can self-consistently drive the outflow along the prescribed magnetic field is calculated; these solutions are found by assuming a polytropic index that depends on position. It is shown that provided the wind is properly collimated unlike the outflows along dipolar magnetic configurations, there now exists a single wind-type solution even in the rotationless case. The behavior of the rotationless solutions is fully explored by varying the wind parameters. The sample of solutions presented illustrates the fact that the asymptotic regime of a rotational atmosphere approaches that of a rotationless atmosphere because, as is shown, the azimuthal velocity decreases faster than the poloidal velocity in the wind region. The topology of the solutions for rotating plasma outflows is discussed in detail. Within this framework, the magnetic field line deflection is related to a curvature parameter. Although its interesting values are those close to zero, the curvature parameter takes, in principle, all its allowed values. It is shown that there exists a limiting curvature in order for the stellar wind to have a physical meaning. The general analysis of θ-dependent Mach-Alfvén surfaces will be presented in a later paper. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_0004637X_v449_n2_p745_Rotstein
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic MHD
Plasmas
Stars: mass loss
spellingShingle MHD
Plasmas
Stars: mass loss
Rotstein, N.O.
Fontán, C.F.
Magnetohydrodynamic stellar wind solutions in curved magnetic fields
topic_facet MHD
Plasmas
Stars: mass loss
description This paper generalizes the analytic class of magnetohydrodynamic (MHD) solutions introduced by Low and Tsinganos for steady, rotating, axisymmetric stellar winds embedded in partially open magnetic fields. The collimation of the outflow is achieved by assuming a magnetic configuration that not only has the property that its field lines are poleward deflected but also includes as particular cases the streamline geometries proposed by other authors. The full MHD equations are reduced to a set of second-order, radial, ordinary differential equations by a suitable choice of the angular dependence of the dynamic and thermodynamic variables. In particular, spherically symmetric Mach-Alfvén surfaces are assumed. The required heating distribution that can self-consistently drive the outflow along the prescribed magnetic field is calculated; these solutions are found by assuming a polytropic index that depends on position. It is shown that provided the wind is properly collimated unlike the outflows along dipolar magnetic configurations, there now exists a single wind-type solution even in the rotationless case. The behavior of the rotationless solutions is fully explored by varying the wind parameters. The sample of solutions presented illustrates the fact that the asymptotic regime of a rotational atmosphere approaches that of a rotationless atmosphere because, as is shown, the azimuthal velocity decreases faster than the poloidal velocity in the wind region. The topology of the solutions for rotating plasma outflows is discussed in detail. Within this framework, the magnetic field line deflection is related to a curvature parameter. Although its interesting values are those close to zero, the curvature parameter takes, in principle, all its allowed values. It is shown that there exists a limiting curvature in order for the stellar wind to have a physical meaning. The general analysis of θ-dependent Mach-Alfvén surfaces will be presented in a later paper.
format JOUR
author Rotstein, N.O.
Fontán, C.F.
author_facet Rotstein, N.O.
Fontán, C.F.
author_sort Rotstein, N.O.
title Magnetohydrodynamic stellar wind solutions in curved magnetic fields
title_short Magnetohydrodynamic stellar wind solutions in curved magnetic fields
title_full Magnetohydrodynamic stellar wind solutions in curved magnetic fields
title_fullStr Magnetohydrodynamic stellar wind solutions in curved magnetic fields
title_full_unstemmed Magnetohydrodynamic stellar wind solutions in curved magnetic fields
title_sort magnetohydrodynamic stellar wind solutions in curved magnetic fields
url http://hdl.handle.net/20.500.12110/paper_0004637X_v449_n2_p745_Rotstein
work_keys_str_mv AT rotsteinno magnetohydrodynamicstellarwindsolutionsincurvedmagneticfields
AT fontancf magnetohydrodynamicstellarwindsolutionsincurvedmagneticfields
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