Whitepaper #209 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; solar physics; emerging opportunities.
We present a strategy for answering the question of how the magnetically closed corona is heated. It is focused on the goal of constructing physics-based models that can nowcast and eventually forecast the solar spectral irradiance for space weather operations. Such models will also be invaluable for studying the spectral irradiance from other stars and its effect on the development of life.