Does the solar granulation change with the activity cycle?

¹ Institut de Recherche en Astrophysique et Planétologie de l’Observatoire Midi-Pyrénées, Université de Toulouse, CNRS, section Observatoire du Pic du Midi, 57 Avenue d’Azereix, 65008 Tarbes, France
e-mail: muller@ast.obs-mip.eu
² Institut für Physik, Karl-Franzen Universität Graz, Universitätsplatz 5, 8010 Graz, Austria
e-mail: arnold.hanslmeier@uni-graz.at
³ Kwasan and Hida Observatories, Kyoto University, Gifu, Japan

Received: 11 October 2017
Accepted: 5 April 2018

Abstract

Context. Knowledge of the variation of the solar granulation properties (contrast and scale) with the 11-yr activity cycle is useful for a better understanding of the interaction between magnetic field and convection at global or local scales. A varying granulation may also contribute to irradiance variations and affect the p-mode damping rates and lifetimes.

Aims. HINODE/SOT blue continuum images taken in the frame of the synoptic program at the disk center on a daily basis between November 2006 and February 2016 are used. This period covers the minimum of activity between cycles 23 and 24 and the maximum of cycle 24.

Methods. The sharpness of a significant number of images was reduced because of instrumental aberrations or inaccurate focusing. Only the sharpest images were selected for this investigation.

Results. To be detectable with HINODE/SOT images, the variation of the granulation contrast and of the granulation scale at the disk center should have been larger than 3%. As it is not the case, it is concluded that they varied by less than 3% through the weak cycle 24.