Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging (ZDI)
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We are reaching the point where spectropolarimetric surveys have run for long enough to reveal solar-like magnetic activity cycles. In this paper we investigate what would be the best strategy to identify solar-like magnetic cycles and ask which large-scale magnetic field parameters best follow a solar-type magnetic cycle and are observable with the Zeeman-Doppler-Imaging (ZDI) technique. We approach these questions using the 3D non-potential flux transport simulations of Yeates & Mackay (2012) modelling the solar vector magnetic field over 15 years (centred on solar cycle 23). The flux emergence profile was extracted from solar synoptic maps and used as input for a photospheric flux transport model in combination with a non-potential coronal evo- lution model. We synthesise spectropolarimetric data from the simulated maps and reconstruct them using ZDI. The ZDI observed solar cycle is set into the context of other cool star observations and we present observable trends of the magnetic field topology with time, sunspot number and S-index. We find that the axisymmetric en- ergy fraction is the best parameter of the ZDI detectable large-scale field to trace solar-like cycles. Neither the surface averaged large-scale field or the total magnetic energy is appropriate. ZDI seems also to be able to recover the increase of the toroidal energy with S-index. We see further that ZDI might unveil hints of the dynamo modes that are operating and of the global properties of the small-scale flux emergence like active latitudes
Lehmann , L T , Hussain , G A J , Vidotto , A , Jardine , M M & Mackay , D H 2020 , ' Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging (ZDI) ' , Monthly Notices of the Royal Astronomical Society .
Monthly Notices of the Royal Astronomical Society
Copyright © 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://academic.oup.com/mnras
DescriptionFunding: UK Science & Technology Facilities Council (STFC) (ST/M001296/1) (MJM). UK STFC and the ERC (Synergy Grant: WHOLE SUN, Grant Agreement No. 810218) (DHM).
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