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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Detalles Bibliográficos
Publicado: 2000
Materias:
Sun: corona
Sun: magnetic fields
Sun: X-rays, gamma rays
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v530_n2PART1_p999_Mandrini
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 paper:paper_0004637X_v530_n2PART1_p999_Mandrini
record_format dspace
spelling paper:paper_0004637X_v530_n2PART1_p999_Mandrini2023-06-08T14:28:41Z Magnetic field and plasma scaling laws: Their implications for coronal heating models 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. 2000 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v530_n2PART1_p999_Mandrini 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
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.
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
publishDate 2000
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v530_n2PART1_p999_Mandrini
http://hdl.handle.net/20.500.12110/paper_0004637X_v530_n2PART1_p999_Mandrini
_version_ 1768545581907574784

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