Magnetic field and plasma scaling laws: Their implications for coronal heating models

In order to test different models of coronal heating, we have investigated how the magnetic field strength of coronal flux tubes depends on the end-to-end length of the tube. Using photospheric magnetograms from both observed and idealized active regions, we computed potential, linear force-free, an...

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Autores principales:	Mandrini, C.H., Démoulin, P., Klimchuk, J.A.
Formato:	JOUR
Materias:	Sun: corona Sun: magnetic fields Sun: X-rays, gamma rays
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_0004637X_v530_n2PART1_p999_Mandrini
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	todo:paper_0004637X_v530_n2PART1_p999_Mandrini
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spelling	todo:paper_0004637X_v530_n2PART1_p999_Mandrini2023-10-03T14:01:47Z Magnetic field and plasma scaling laws: Their implications for coronal heating models Mandrini, C.H. Démoulin, P. Klimchuk, J.A. Sun: corona Sun: magnetic fields Sun: X-rays, gamma rays In order to test different models of coronal heating, we have investigated how the magnetic field strength of coronal flux tubes depends on the end-to-end length of the tube. Using photospheric magnetograms from both observed and idealized active regions, we computed potential, linear force-free, and magnetostatic extrapolation models. For each model, we then determined the average coronal field strength, 〈B〉, in approximately 1000 individual flux tubes with regularly spaced footpoints. Scatter plots of 〈B〉; versus length, L, are characterized by a flat section for small L and a steeply declining section for large L. They are well described by a function of the form log 〈B〉 = C1 + C2 log L + C3/2 log (L2 + S2), where C2 ≈ 0, - 3 ≤ C3 ≤ - 1, and 40 ≤ S ≤ 240 Mm is related to the characteristic size of the active region. There is a tendency for the magnitude of C3 to decrease as the magnetic complexity of the region increases. The average magnetic energy in a flux tube, 〈B;2〉, exhibits a similar behavior, with only C3 being significantly different. For flux tubes of intermediate length, 50 ≤ L ≤ 300 Mm, corresponding to the soft X-ray loops in a study by Klimchuk & Porter (1995), we find a universal scaling law of the form 〈B〉 ∞ Lδ, where δ = -0.88 ± 0.3. By combining this with the Klimchuk & Porter result that the heating rate scales as L-2, we can test different models of coronal heating. We find that models involving the gradual stressing of the magnetic field, by slow footpoint motions, are in generally better agreement with the observational constraints than are wave heating models. We conclude, however, that the theoretical models must be more fully developed and the observational uncertainties must be reduced before any definitive statements about specific heating mechanisms can be made. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_0004637X_v530_n2PART1_p999_Mandrini
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: corona Sun: magnetic fields Sun: X-rays, gamma rays
spellingShingle	Sun: corona Sun: magnetic fields Sun: X-rays, gamma rays Mandrini, C.H. Démoulin, P. Klimchuk, J.A. Magnetic field and plasma scaling laws: Their implications for coronal heating models
topic_facet	Sun: corona Sun: magnetic fields Sun: X-rays, gamma rays
description	In order to test different models of coronal heating, we have investigated how the magnetic field strength of coronal flux tubes depends on the end-to-end length of the tube. Using photospheric magnetograms from both observed and idealized active regions, we computed potential, linear force-free, and magnetostatic extrapolation models. For each model, we then determined the average coronal field strength, 〈B〉, in approximately 1000 individual flux tubes with regularly spaced footpoints. Scatter plots of 〈B〉; versus length, L, are characterized by a flat section for small L and a steeply declining section for large L. They are well described by a function of the form log 〈B〉 = C1 + C2 log L + C3/2 log (L2 + S2), where C2 ≈ 0, - 3 ≤ C3 ≤ - 1, and 40 ≤ S ≤ 240 Mm is related to the characteristic size of the active region. There is a tendency for the magnitude of C3 to decrease as the magnetic complexity of the region increases. The average magnetic energy in a flux tube, 〈B;2〉, exhibits a similar behavior, with only C3 being significantly different. For flux tubes of intermediate length, 50 ≤ L ≤ 300 Mm, corresponding to the soft X-ray loops in a study by Klimchuk & Porter (1995), we find a universal scaling law of the form 〈B〉 ∞ Lδ, where δ = -0.88 ± 0.3. By combining this with the Klimchuk & Porter result that the heating rate scales as L-2, we can test different models of coronal heating. We find that models involving the gradual stressing of the magnetic field, by slow footpoint motions, are in generally better agreement with the observational constraints than are wave heating models. We conclude, however, that the theoretical models must be more fully developed and the observational uncertainties must be reduced before any definitive statements about specific heating mechanisms can be made.
format	JOUR
author	Mandrini, C.H. Démoulin, P. Klimchuk, J.A.
author_facet	Mandrini, C.H. Démoulin, P. Klimchuk, J.A.
author_sort	Mandrini, C.H.
title	Magnetic field and plasma scaling laws: Their implications for coronal heating models
title_short	Magnetic field and plasma scaling laws: Their implications for coronal heating models
title_full	Magnetic field and plasma scaling laws: Their implications for coronal heating models
title_fullStr	Magnetic field and plasma scaling laws: Their implications for coronal heating models
title_full_unstemmed	Magnetic field and plasma scaling laws: Their implications for coronal heating models
title_sort	magnetic field and plasma scaling laws: their implications for coronal heating models
url	http://hdl.handle.net/20.500.12110/paper_0004637X_v530_n2PART1_p999_Mandrini
work_keys_str_mv	AT mandrinich magneticfieldandplasmascalinglawstheirimplicationsforcoronalheatingmodels AT demoulinp magneticfieldandplasmascalinglawstheirimplicationsforcoronalheatingmodels AT klimchukja magneticfieldandplasmascalinglawstheirimplicationsforcoronalheatingmodels
_version_	1807322981489180672

Magnetic field and plasma scaling laws: Their implications for coronal heating models

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