The Flare Irradiance Spectral Model (FISM) is an important tool for
estimating solar variability for a myriad of space weather research
studies and applications, and FISM Version 2 (FISM2) has recently been
been released. FISM2 is an empirical model of the solar ultraviolet
irradiance created to fill spectral and temporal gaps in the
measurements, where these measurements are infrequent as they need to be
made from space due to their absorption in the planetary atmospheres.
FISM2 estimates solar ultraviolet irradiance variations due to solar
cycle, solar rotation, and solar flare variations. The major improvement
provided by FISM2 is that it is based on multiple new, more accurate
instruments that have now captured almost a full solar cycle and
thousands of flares, drastically improving the accuracy of the modeled
FISM2 solar irradiance spectra. FISM2 is also improved to 0.1 nm
spectral bins across the same 0-190 nm spectral range, and is already
being used in research to estimate space weather changes due to solar
irradiance variability in planetary thermospheres and ionospheres.