Whitepaper #020 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: space weather applications; basic research. Additional topics: space weather research/applications/operations pipeline; ground-based missions/projects; solar physics.
We describe the importance of imaging spectroscopy, based on a tunable filter approach, for addressing key science goals of the solar physics community in studying the thermodynamics and magnetic field of the chromosphere and corona. We outline some basic requirements for such an instrument and identify some possible technical approaches.