  Energy stored in the magnetic field in the solar atmosphere above active
regions is a key driver of all solar activity (e.g., solar flares and coronal
mass ejections), some of which can affect life on Earth. Radio observations
provide a unique diagnostic of the coronal magnetic fields that make them a
critical tool for the study of these phenomena, using the technique of
broadband radio imaging spectropolarimetry. Observations with the ngVLA will
provide unique observations of coronal magnetic fields and their evolution, key
inputs and constraints for MHD numerical models of the solar atmosphere and
eruptive processes, and a key link between lower layers of the solar atmosphere
and the heliosphere. In doing so they will also provide practical "research to
operations" guidance for space weather forecasting.
