Solar irradiance is the primary energy input to the thermosphere and ionosphere system. Solar irradiance (soft X-ray, extreme ultra-violet, and far ultra-violet) ionizes, dissociates, and excites the thermospheric constituents, create the ionosphere, and heat the thermosphere. In this presentation, we discuss solar irradiance effects on the thermosphere-ionosphere-mesosphere system on time scales from solar rotation, season, solar cycle, to climate change, using both data and model simulations. The data sets will include neutral density derived from satellite drag, and thermosphere composition data from TIMED/GUVI and NASA GOLD. Modeling results are from the Whole Atmosphere Community Climate Model – eXtended (WACCM-X), the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM), and the NRLMSISE-00 empirical model.