The magnetically quiet solar surface dominates HARPS-N solar RVs during low activity
Abstract
Using images from the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory, we extract the radial velocity (RV) signal arising from the suppression of convective blueshift and from bright faculae and dark sunspots transiting the rotating solar disc. We remove these rotationally modulated magnetic-activity contributions from simultaneous RVs observed by the HARPS-N (High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) solar feed to produce an RV time series arising from the magnetically quiet solar surface (the ‘inactive-region RVs’). We find that the level of variability in the inactive-region RVs remains constant over the almost 7-yr baseline and shows no correlation with well-known activity indicators. With an root-mean-square scatter of roughly 1 ms-1, the inactive-region RV time series dominates the total RV variability budget during the decline of solar cycle 24. Finally, we compare the variability amplitude and time-scale of the inactive-region RVs with simulations of supergranulation. We find consistency between the inactive-region RV and simulated time series, indicating that supergranulation is a significant contribution to the overall solar RV variability, and may be the main source of variability towards solar minimum. This work highlights supergranulation as a key barrier to detecting Earth twins.
Citation
Lakeland , B S , Naylor , T , Haywood , R D , Meunier , N , Rescigno , F , Dalal , S , Mortier , A , Thompson , S J , Cameron , A C , Dumusque , X , López-Morales , M , Pepe , F , Rice , K , Sozzetti , A , Udry , S , Ford , E , Ghedina , A & Lodi , M 2024 , ' The magnetically quiet solar surface dominates HARPS-N solar RVs during low activity ' , Monthly Notices of the Royal Astronomical Society , vol. 527 , no. 3 , pp. 7681–7691 . https://doi.org/10.1093/mnras/stad3723
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Description
Funding: ACC acknowledges support from STFC consolidated grant number ST/V000861/1 and UKSA grant number ST/R003203/1. RDH and SD were funded by the STFC’s Ernest Rutherford Fellowship (grant number ST/V004735/1). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement SCORE No. 851555). KR acknowledges support from STFC consolidated grant number ST/V000594/1.Collections
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