Helium line formation and abundance during a C-class flare

During a coordinated campaign that took place in 2001 May, a C-class flare was observed both with SOHO instruments and with the Dunn Solar Telescope of the National Solar Observatory at Sacramento Peak. In two previous papers we described the observations and discussed some dynamical aspects of the...

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Publicado:	2008
Materias:	Sun: abundances Sun: activity Sun: chromosphere
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v681_n1_p650_Andretta http://hdl.handle.net/20.500.12110/paper_0004637X_v681_n1_p650_Andretta
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_0004637X_v681_n1_p650_Andretta
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spelling	paper:paper_0004637X_v681_n1_p650_Andretta2023-06-08T14:28:56Z Helium line formation and abundance during a C-class flare Sun: abundances Sun: activity Sun: chromosphere During a coordinated campaign that took place in 2001 May, a C-class flare was observed both with SOHO instruments and with the Dunn Solar Telescope of the National Solar Observatory at Sacramento Peak. In two previous papers we described the observations and discussed some dynamical aspects of the earlier phases of the flare, as well as the helium line formation in the active region prior to the event. Here we extend the analysis of the helium line formation to the later phases of the flare in two different locations of the flaring area. We have devised a new technique, exploiting all available information from various SOHO instruments, to determine the spectral distribution of the photoionizing EUV radiation produced by the corona overlying the two target regions. In order to find semiempirical models matching all of our observables, we analyzed the effect on the calculated helium spectrum, both of AHe (the He abundance) and of the uncertainties in the incident EUV radiation (level and spectral distribution). We found that the abundance has in most cases (but not in all) a larger effect than the coronal back-radiation. The result of our analysis is that, considering the error of the measured lines and adopting our best estimate for the coronal EUV illumination, the value AHe = 0.075 ± 0.010 in the chromosphere (for T > 6300 K) and transition region yields reasonably good matches for all the observed lines. This value is marginally consistent with the most commonly accepted photospheric value, A He = 0.085. © 2008. The American Astronomical Society. All rights reserved. 2008 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v681_n1_p650_Andretta http://hdl.handle.net/20.500.12110/paper_0004637X_v681_n1_p650_Andretta
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Sun: abundances Sun: activity Sun: chromosphere
spellingShingle	Sun: abundances Sun: activity Sun: chromosphere Helium line formation and abundance during a C-class flare
topic_facet	Sun: abundances Sun: activity Sun: chromosphere
description	During a coordinated campaign that took place in 2001 May, a C-class flare was observed both with SOHO instruments and with the Dunn Solar Telescope of the National Solar Observatory at Sacramento Peak. In two previous papers we described the observations and discussed some dynamical aspects of the earlier phases of the flare, as well as the helium line formation in the active region prior to the event. Here we extend the analysis of the helium line formation to the later phases of the flare in two different locations of the flaring area. We have devised a new technique, exploiting all available information from various SOHO instruments, to determine the spectral distribution of the photoionizing EUV radiation produced by the corona overlying the two target regions. In order to find semiempirical models matching all of our observables, we analyzed the effect on the calculated helium spectrum, both of AHe (the He abundance) and of the uncertainties in the incident EUV radiation (level and spectral distribution). We found that the abundance has in most cases (but not in all) a larger effect than the coronal back-radiation. The result of our analysis is that, considering the error of the measured lines and adopting our best estimate for the coronal EUV illumination, the value AHe = 0.075 ± 0.010 in the chromosphere (for T > 6300 K) and transition region yields reasonably good matches for all the observed lines. This value is marginally consistent with the most commonly accepted photospheric value, A He = 0.085. © 2008. The American Astronomical Society. All rights reserved.
title	Helium line formation and abundance during a C-class flare
title_short	Helium line formation and abundance during a C-class flare
title_full	Helium line formation and abundance during a C-class flare
title_fullStr	Helium line formation and abundance during a C-class flare
title_full_unstemmed	Helium line formation and abundance during a C-class flare
title_sort	helium line formation and abundance during a c-class flare
publishDate	2008
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v681_n1_p650_Andretta http://hdl.handle.net/20.500.12110/paper_0004637X_v681_n1_p650_Andretta
_version_	1768542766641446912

Helium line formation and abundance during a C-class flare

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