Solar cycle variation in Sun-as-a-star Ca II 854.2 nm bisectors

Abstract

The bisector of the strong chromospheric Ca II 854.2 nm line has an inverse-C shape the cause of which is not yet fully understood. We show that the amplitude of the bisector in Sun-as-a-star observations exhibits a solar cycle variation with smaller amplitudes during highest activity. The line core intensity is lower during solar minima while the part of the bisector most sensitive to the line core shows no systematic change with activity. Our results support the use of Ca II 854.2 nm bisectors in studying the relationship between convection and magnetic fields, not only in the Sun but in other stars as well.

Accepted to ApJ

References in corpus (2)

• Re-assessing the radial-velocity evidence for planets around CoRoT-7
• Bisectors of the cross-correlation function applied to stellar spectra. Discriminating stellar activity, oscillations and planets

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• Ca ii 854.2 nm in an enhanced network region simulated with MURaM-ChE
• EMISSA: Exploring millimetre indicators of solar-stellar activity III. Comparison of Ca II indices and millimetre continua in a 3D model atmosphere