Knowledge of the structure and evolution of the magnetic field of the solar corona is important for investigating and understanding the origins of space weather. Although the coronal field remains difficult to measure directly, a modeled coronal field may be calculated from available photospheric boundary data. One class of models assumes that the corona, due to its low plasma beta, is free of Lorentz forces. Such nonlinear force-free field (NLFFF) models, when they are able to be computed, provide insight into coronal energetics without having to solve the full magneto-hydrodynamic equations, which at present are computationally infeasible at spatial resolutions needed for detailed analyses of active-region dynamics.

However, past research has established that NLFFF models are beset by problems that preclude their use on a regular basis. Some of these problems result from limitations in the data, while others are due to the models being overly idealized. In recent years, advances in modeling techniques combined with new instrumentation and data have enabled many of these issues to be addressed. This ISSI International Team seeks to develop, test, and assess the next generation of NLFFF models to meet twice in the next two years. These models will help achieve a better understanding of the energetics and evolution of the solar corona.