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Internal magnetic fields inferred from helioseismic data
Author(s) -
Baldner C.S.,
Antia H.M.,
Basu S.,
Larson T.P.
Publication year - 2010
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.201011418
Subject(s) - helioseismology , physics , toroid , dipole , magnetic field , field (mathematics) , toroidal field , computational physics , toroidal and poloidal , astrophysics , field strength , plasma , nuclear physics , quantum mechanics , mathematics , pure mathematics
Measuring the internal solar magnetic fields and how they change over the course of a solar cycle is one of the key aims of helioseismology. We present the results of attempts to model the global mode splitting coefficients over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large‐scale magnetic field. The first results using only the a 2 coefficients show that the data are best fit by a combination of a poloidal field and a double‐peaked near‐surface toroidal field. The toroidal fields are centered at r 0 = 0.999 R ⊙ and r 0 = 0.996 R ⊙ and are confined to the near‐surface layers. The poloidal field is a dipole field. The peak strength of the poloidal field is 124 ± 17 G. The toroidal field peaks at 380 ± 30 G and 1.4 ± 0.2 kG for the shallower and deeper fields, respectively. The field strengths are highly correlated with surface activity. We also examine the differences between the minima at the beginning and the end of solar cycle 23 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)