Mon. Not. R. Astron. Soc., 480, 477-487 (2018/October-2)
The magnetic field vector of the Sun-as-a-star - II. Evolution of the large-scale vector field through activity cycle 24.
VIDOTTO A.A., LEHMANN L.T., JARDINE M. and PEVTSOV A.A.
Abstract (from CDS):
In this 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 January to 2018 April. 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 per cent 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 (<B_ tor_2>) and poloidal (<B_ pol_2>) energies are related as <B_ tor_2>∝<^B_ pol_2>1.38±0.04^. Similar to the stellar sample, the large-scale field of the Sun shows a lack of toroidal non-axisymmetric field.
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
methods: analytical - magnetic topology - surface magnetism - magnetic fields
View the reference in ADS
To bookmark this query, right click on this link: simbad:2018MNRAS.480..477V and select 'bookmark this link' or equivalent in the popup menu