S. Marchenko, M.T. DeLand, D. Choudary, G. Kopp

We investigate the variability of solar Balmer lines (H-α, -β, -γ, -δ) from space-borne radiometers (OSIRIS, SCIAMACHY, OMI, GOME-2) and ground-based NSO/ISS spectrograph data, linking the observed changes to the solar disk's magnetic features. On solar-rotational timescales (about 1 month), the Balmer-line activity indices (defined as line-core to line-wing ratios) closely follow variations in the total solar irradiance (which is predominantly photospheric), thus frequently (specifically, during passages of sunspot groups) deviating from behavior of activity indices that track chromospheric activity levels. On longer timescales, the correlation with chromospheric indices increases, with periods of low- or even anti-correlation found at intermediate (months to years) timescales. Comparison of these observations with estimates from semi-empirical irradiance reconstructions helps quantify the contributions of different magnetic and quiet features. We conclude that both the lower sensitiv