Long-Term Datasets for the Understanding of Solar and Stellar Magnetic Cycles Proceedings IAU Symposium No. 340, 2018 D. Banerjee, J. Jiang, K. Kusano & S. Solanki, eds. c  International Astronomical Union 2018 doi:10.1017/S1743921318001369 Kyiv monitoring program of spectral line variations with the 11-year cycle Nataliia Shchukina 1 , Sergej Osipov 1 , Roman Kostyk 1 and Myroslav Stodilka 2 1 Main Astronomical Observatory, National Academy of Sciences, 27 Zabolotnogo str., Kyiv, 03143, Ukraine email: shchukin@mao.kiev.ua 2 Astronomical Observatory, Ivan Franko National University, 8 Kyryla and Mefodiya str., Lviv, 79005, Ukraine email: sun@astro.franko.lviv.ua Abstract. Kyiv program of monitoring of long-term variation of solar spectral lines at the horizontal solar telescope of the Main Astronomical Observatory of Ukraine is described. The aim of the program is to clarify the issue how the physical parameters of the quiet solar atmosphere change over the 11-year cycle of solar activity. The diagnostics of the atmospheric variation includes analysis of more than 40 spectral lines of neutral and ionized chemical elements observed at the solar disk and at the limb near north and south poles with high spectral resolution. The results of monitoring show that during 2012–2017 a line core depths and a line full widths at half maximum respond to the cycle modulation of the global unsigned magnetic field of the Sun. Such a correlation can be explained by assuming that temperature gradient of the solar photosphere is growing with solar activity. Keywords. Sun: atmosphere, line: profiles, line: formation, instrumentation: spectrographs, techniques: spectroscopic 1. Introduction The first monitoring programs aimed to study changes in spectral lines with 11-year cycle of solar activity started in the mid-fifties of the last century. In particular, Krat & Kokhan (1984) published results of observations of selected spectral lines carried out since 1969. They found that changes in the central line intensities during the 11-year cycle occur within 1%. For many years Livingston & Holweger (1982); Doyle et al. (2001); Livingston et al. (2007); Livingston et al. (2010) monitored chromospheric and photospheric spectral lines, integrated over the full disk (i.e., “the Sun as a star”) and some of them for a small circular region near the center of the solar disk. After over 30 years of observations Livingston et al. (2007) concluded that the “basal quiet atmosphere is unaffected by cycle magnetism within our observational error”. Recently, Danilovic et al. (2016) pointed out at a high correlation of the magnitude of solar cycle variations between the full-disk observed and reconstructed change in the Mn i 539.5 nm line parameters. Since 2006 Synoptic Optical Long-term Investigations of the Sun (SOLIS) provides autonomous full- disk spectral, magnetic, and imaging measurements to help understanding solar activity and its effect on the Earth’s climate and atmosphere (Keller et al. 2003; SOLIS 2018). It should be noted that the Sun as a star monitoring of spectral lines does not allow us to answer the question whether the physical parameters of the quiet solar atmosphere outside active regions change over the 11-year cycle of the solar activity. Kyiv program of long-term monitoring of solar spectral lines variation aims to clarify this question. 31 https://doi.org/10.1017/S1743921318001369 Published online by Cambridge University Press