CLOUDY-90 - NUMERICAL-SIMULATION OF PLASMAS AND THEIR SPECTRA

CLOUDY is a large-scale spectral synthesis code designed to simulate f ully physical conditions within an astronomical plasma and then predic t the emitted spectrum. Here we describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and num erical methods that have affected predictions since the last publicly available version, C84. The computational methods and uncertainties ar e outlined together with the direction future development will take. T he code is freely available and is widely used in the analysis and int erpretation of emission-line spectra. Web access to the Fortran source for CLOUDY, its documentation Hazy, and an independent electronic for m of the atomic database is also described.