Oxygen abundance in coronal streamers

In a previous work we developed a stationary proton-electron MHD model of the solar corona, suitable for the minimum-activity epochs. In the present work, we use empirically derived information from the past solar minimum for the oxygen parameters (temperatures and outflow velocity) to develop an ox...

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Autores principales: Vásquez, A.M., Raymond, J.C.
Formato: JOUR
Materias:
Solar wind
Sun: abundances
Sun: corona
Sun: UV radiation
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_0004637X_v619_n2I_p1132_Vasquez
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_0004637X_v619_n2I_p1132_Vasquez2023-10-03T14:01:59Z Oxygen abundance in coronal streamers Vásquez, A.M. Raymond, J.C. Solar wind Sun: abundances Sun: corona Sun: UV radiation In a previous work we developed a stationary proton-electron MHD model of the solar corona, suitable for the minimum-activity epochs. In the present work, we use empirically derived information from the past solar minimum for the oxygen parameters (temperatures and outflow velocity) to develop an oxygen model in the frame of our previous model. Solar and Heliospheric Observatory UVCS observations of past minimum coronal streamers in the O VI λ1032 and O VI λ1037 lines have revealed that oxygen abundances are very much depleted within the stable closed-field regions of the quiescent streamers. This characteristic appears as a relatively dark region, often seen in the core of the quiescent equatorial streamers when imaged in oxygen lines. Using the oxygen abundance as a free parameter, we compute the expected O VI line emissivities from our models and synthesize images considering the projection effects in detail. We find here that, in order to obtain oxygen images with dark streamer cores similar to those observed, very low element abundances have to be assumed. The required depletion factors are lower than previous estimates that do not account for projection effects, which is especially important at 1.75 R⊙ and higher. © 2005. The American Astronomical Society. All rights reserved. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_0004637X_v619_n2I_p1132_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 Solar wind
Sun: abundances
Sun: corona
Sun: UV radiation
spellingShingle Solar wind
Sun: abundances
Sun: corona
Sun: UV radiation
Vásquez, A.M.
Raymond, J.C.
Oxygen abundance in coronal streamers
topic_facet Solar wind
Sun: abundances
Sun: corona
Sun: UV radiation
description In a previous work we developed a stationary proton-electron MHD model of the solar corona, suitable for the minimum-activity epochs. In the present work, we use empirically derived information from the past solar minimum for the oxygen parameters (temperatures and outflow velocity) to develop an oxygen model in the frame of our previous model. Solar and Heliospheric Observatory UVCS observations of past minimum coronal streamers in the O VI λ1032 and O VI λ1037 lines have revealed that oxygen abundances are very much depleted within the stable closed-field regions of the quiescent streamers. This characteristic appears as a relatively dark region, often seen in the core of the quiescent equatorial streamers when imaged in oxygen lines. Using the oxygen abundance as a free parameter, we compute the expected O VI line emissivities from our models and synthesize images considering the projection effects in detail. We find here that, in order to obtain oxygen images with dark streamer cores similar to those observed, very low element abundances have to be assumed. The required depletion factors are lower than previous estimates that do not account for projection effects, which is especially important at 1.75 R⊙ and higher. © 2005. The American Astronomical Society. All rights reserved.
format JOUR
author Vásquez, A.M.
Raymond, J.C.
author_facet Vásquez, A.M.
Raymond, J.C.
author_sort Vásquez, A.M.
title Oxygen abundance in coronal streamers
title_short Oxygen abundance in coronal streamers
title_full Oxygen abundance in coronal streamers
title_fullStr Oxygen abundance in coronal streamers
title_full_unstemmed Oxygen abundance in coronal streamers
title_sort oxygen abundance in coronal streamers
url http://hdl.handle.net/20.500.12110/paper_0004637X_v619_n2I_p1132_Vasquez
work_keys_str_mv AT vasquezam oxygenabundanceincoronalstreamers
AT raymondjc oxygenabundanceincoronalstreamers
_version_ 1807323989455929344

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