The effect of proton temperature anisotropy on the solar minimum corona and wind

A semiempirical, axisymmetric model of the solar minimum corona is developed by solving the equations for conservation of mass and momentum with prescribed anisotropic temperature distributions. In the high-latitude regions, the proton temperature anisotropy is strong and the associated mirror force...

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Autores principales:	Vásquez, A.M., Van Ballegooijen, A.A., Raymond, J.C.
Formato:	JOUR
Materias:	MHD Solar wind Sun: corona Sun: magnetic fields Sun: UV radiation
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_0004637X_v598_n2I_p1361_Vasquez
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	todo:paper_0004637X_v598_n2I_p1361_Vasquez
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spelling	todo:paper_0004637X_v598_n2I_p1361_Vasquez2023-10-03T14:01:55Z The effect of proton temperature anisotropy on the solar minimum corona and wind Vásquez, A.M. Van Ballegooijen, A.A. Raymond, J.C. MHD Solar wind Sun: corona Sun: magnetic fields Sun: UV radiation A semiempirical, axisymmetric model of the solar minimum corona is developed by solving the equations for conservation of mass and momentum with prescribed anisotropic temperature distributions. In the high-latitude regions, the proton temperature anisotropy is strong and the associated mirror force plays an important role in driving the fast solar wind; the critical point where the outflow velocity equals the parallel sound speed (v = c ∥) is reached already at 1.5 R⊙ from Sun center. The slow wind arises from a region with open-field lines and weak anisotropy surrounding the equatorial streamer belt. The model parameters were chosen to reproduce the observed latitudinal extent of the equatorial streamer in the corona and at large distance from the Sun. We find that the magnetic cusp of the closed-field streamer core lies at about 1.95 R⊙. The transition from fast to slow wind is due to a decrease in temperature anisotropy combined with the nonmonotonic behavior of the nonradial expansion factor in flow tubes that pass near the streamer cusp. In the slow wind, the plasma β is of order unity and the critical point lies at about 5 R ⊙, well beyond the magnetic cusp. The predicted outflow velocities are consistent with O5+ Doppler dimming measurements from UVCS/SOHO. We also find good agreement with polarized brightness (pB) measurements from LASCQ/SOHO and H I Lyα images from UVCS/SOHO. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_0004637X_v598_n2I_p1361_Vasquez
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 Solar wind Sun: corona Sun: magnetic fields Sun: UV radiation
spellingShingle	MHD Solar wind Sun: corona Sun: magnetic fields Sun: UV radiation Vásquez, A.M. Van Ballegooijen, A.A. Raymond, J.C. The effect of proton temperature anisotropy on the solar minimum corona and wind
topic_facet	MHD Solar wind Sun: corona Sun: magnetic fields Sun: UV radiation
description	A semiempirical, axisymmetric model of the solar minimum corona is developed by solving the equations for conservation of mass and momentum with prescribed anisotropic temperature distributions. In the high-latitude regions, the proton temperature anisotropy is strong and the associated mirror force plays an important role in driving the fast solar wind; the critical point where the outflow velocity equals the parallel sound speed (v = c ∥) is reached already at 1.5 R⊙ from Sun center. The slow wind arises from a region with open-field lines and weak anisotropy surrounding the equatorial streamer belt. The model parameters were chosen to reproduce the observed latitudinal extent of the equatorial streamer in the corona and at large distance from the Sun. We find that the magnetic cusp of the closed-field streamer core lies at about 1.95 R⊙. The transition from fast to slow wind is due to a decrease in temperature anisotropy combined with the nonmonotonic behavior of the nonradial expansion factor in flow tubes that pass near the streamer cusp. In the slow wind, the plasma β is of order unity and the critical point lies at about 5 R ⊙, well beyond the magnetic cusp. The predicted outflow velocities are consistent with O5+ Doppler dimming measurements from UVCS/SOHO. We also find good agreement with polarized brightness (pB) measurements from LASCQ/SOHO and H I Lyα images from UVCS/SOHO.
format	JOUR
author	Vásquez, A.M. Van Ballegooijen, A.A. Raymond, J.C.
author_facet	Vásquez, A.M. Van Ballegooijen, A.A. Raymond, J.C.
author_sort	Vásquez, A.M.
title	The effect of proton temperature anisotropy on the solar minimum corona and wind
title_short	The effect of proton temperature anisotropy on the solar minimum corona and wind
title_full	The effect of proton temperature anisotropy on the solar minimum corona and wind
title_fullStr	The effect of proton temperature anisotropy on the solar minimum corona and wind
title_full_unstemmed	The effect of proton temperature anisotropy on the solar minimum corona and wind
title_sort	effect of proton temperature anisotropy on the solar minimum corona and wind
url	http://hdl.handle.net/20.500.12110/paper_0004637X_v598_n2I_p1361_Vasquez
work_keys_str_mv	AT vasquezam theeffectofprotontemperatureanisotropyonthesolarminimumcoronaandwind AT vanballegooijenaa theeffectofprotontemperatureanisotropyonthesolarminimumcoronaandwind AT raymondjc theeffectofprotontemperatureanisotropyonthesolarminimumcoronaandwind AT vasquezam effectofprotontemperatureanisotropyonthesolarminimumcoronaandwind AT vanballegooijenaa effectofprotontemperatureanisotropyonthesolarminimumcoronaandwind AT raymondjc effectofprotontemperatureanisotropyonthesolarminimumcoronaandwind
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The effect of proton temperature anisotropy on the solar minimum corona and wind

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