The magnetic field vector of the Sun-as-a-star – II. Evolution of the large-scale vector field through activity cycle 24
| Autor: | Aline A. Vidotto, Alexei A. Pevtsov, Moira Jardine, L. T. Lehmann |
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| Přispěvatelé: | Science & Technology Facilities Council, University of St Andrews. School of Physics and Astronomy |
| Rok vydání: | 2018 |
| Předmět: |
Scale (ratio)
Library science 01 natural sciences Surface magnetism Physics::Plasma Physics analytical [Methods] 0103 physical sciences QB Astronomy Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Magnetic topology QC QB Physics Solar observatory 010308 nuclear & particles physics DAS Astronomy and Astrophysics QC Physics Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Magnetic fields Physics::Space Physics Activity cycle Vector field Astrophysics::Earth and Planetary Astrophysics Partial support |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 480:477-487 |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/sty1926 |
| Popis: | In the present work, we investigate how the large-scale magnetic field of the Sun, in its three vector components, has evolved during most of cycle 24, from 2010 Jan to 2018 Apr. To filter out the small-scale field of the Sun, present in high-resolution synoptic maps, we use a spherical harmonic decomposition method, which decomposes the solar field in multipoles with different l degrees. By summing together the low-l multipoles, we reconstruct the large-scale field at a resolution similar to observed stellar magnetic fields, which allows the direct comparison between solar and stellar magnetic maps. During cycle 24, the `Sun-as-a-star' magnetic field shows a polarity reversal in the radial and meridional components, but not in the azimuthal component. The large-scale solar field remains mainly poloidal with > 70% of its energy contained in the poloidal component. During its evolution, the large-scale field is more axisymmetric and more poloidal when near minima in sunspot numbers, and with a larger intensity near maximum. There is a correlation between toroidal energy and sunspot number, which indicates that spot fields are major contributors to the toroidal large-scale energy of the Sun. The solar large-scale magnetic properties fit smoothly with observational trends of stellar magnetism reported in See et al. The toroidal (Etor) and poloidal (Epol) energies are related as Etor ~Epol^{1.38 \pm 0.04}. Similar to the stellar sample, the large-scale field of the Sun shows a lack of toroidal non-axisymmetric field. Comment: 11 pages, 9 figures, 3 tables. Accepted to MNRAS |
| Databáze: | OpenAIRE |
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