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Multi-wavelength observations of active galactic nuclei (AGNs) often revealvarious time scales of variability. Among these phenomena, "changing-look AGNs"are extreme cases where broad emission lines become faint/bright or evendisappear/emerge between multi-epoch observations, providing crucialinformation about AGN internal structures. We here focus on "changing-state"AGNs, specifically investigating the transition of optical spectra over yearsto tens of years. Based on the axisymmetric radiation-hydrodynamicalsimulations (Paper I) for the gas dynamics within the dust-sublimation radius,we investigate the spectral properties of ionized gas exposed to the radiationfrom an AGN with a 10^7 Msun supermassive black hole. We find significanttime-dependent variations in the Balmer emission lines by utilizingpost-process pseudo-three-dimensional calculations and the spectral synthesiscode CLOUDY. The equivalent width of Halpha and Hbeta changes by a factor of 3,or the emission lines even disappear during 30 years for the same viewingangle. The time-dependent behaviour arises primarily from gas dynamics,particularly the formation of non-steady, radiation-driven outflows within theinnermost region of the disc (r <10^-3 pc). The intricate interplay betweennon-spherical radiation sources at the core of AGNs and the dynamic behavior ofgas within the dust sublimation radius gives rise to radiation-driven outflows.This non-steady outflow potentially contributes to the observed variability inBalmer line emissions over multi-year timescales in certain AGNs.

Multi-phase gas nature in the sub-pc region of the active galactic nuclei II: Possible origins of the changing-state AGNs