Plasma Simulations that Meet the Challenges of HST & JWST Active Nuclei & Starburst Observations

Recent HST AGN monitoring programs, such as the STORM Campaign, have resulted in the definitive set of emission-line-continuum lag measurements. The goals are to measure the structure of the inner regions of an AGN, understand the physics driving the variability, and use this to place black hole mass determinations on an even firmer footing. Photoionization models make it possible to convert these observations into physical parameters such as cloud density or location. Here I propose to improve the treatment of emission from species like C IV, C III], Mg II, or Fe II in the spectral / plasma simulation code Cloudy. Like all plasma codes, Cloudy uses a modified two-level approximation to solve for the ionization of many-electron ions. I have participated in meetings on modeling Tokamak plasmas, which share many of the properties of the BLR of AGN and have the advantage of being a controlled laboratory environment. These discussions have led to the development of tests to show the density range over which the two-level approximation is valid. It fails at the densities where the strong UV lines form. I will use the atomic data available within the fusion modeling community, along with the methods they have developed, to improve Cloudy models so that they can better inform us of the message in the UV spectrum. The improvements will be part of future releases of Cloudy, which is openly available and updated on a regular basis.