Review of Solar UV and VUV Irradiances and their Effects on the Atmosphere

The solar ultraviolet (UV) and extreme ultraviolet (EUV) irradiances are created in the chromosphere, transition region, and corona within widely different temperature regimes. As a result, the temporal variability and energy content delivered to the top of the Earth's atmosphere differs significantly between lines and continua across this part of the spectrum. These differences introduce a complex and richly diverse composite of energy inputs at the top of the Earth's atmosphere, energy that is available for photoabsorption, photodissociation, and photoionization processes. Particularly susceptible to these UV and EUV energies are the atmospheric constituents that form the stratosphere, mesosphere, and thermosphere as well as the ionosphere. A review of the recent and current measurements, reference spectra, models, surrogates (proxies), and standardization activities that characterize these irradiances is provided. In addition, users of different spectral regions are identified and the challenges that those communities are placing upon new instrumentation and modeling to meet their requirements are outlined.