The magnetically quiet solar surface dominates HARPS-N solar RVs during low activity

Ben S Lakeland*, Tim Naylor, Raphaëlle D Haywood, Nadège Meunier, Federica Rescigno, Shweta Dalal, Annelies Mortier, Samantha J Thompson, Andrew Collier Cameron, Xavier Dumusque, Mercedes López-Morales, Francesco Pepe, Ken Rice, Alessandro Sozzetti, Stéphane Udry, Eric Ford, Adriano Ghedina, Marcello Lodi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
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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.
Original languageEnglish
Pages (from-to)7681–7691
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date1 Dec 2023
Publication statusPublished - 1 Jan 2024


  • Methods: data analysis
  • Techniques: radial velocities
  • Sun: granulation


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