Monday

The solar atmosphere is hotter than predicted by assuming radiative equilibrium. This is most obviously evidenced by the high temperature of the solar corona, but the bulk of the energy deposition already happens down in the much cooler chromosphere. Because of the high chromospheric density the deposited energy is efficiently radiated away and the temperatures are only modestly elevated above the radiative equilibrium value. Canonical estimates of the chromospheric radiative cooling rate from the seventies and early eighties, based on spatially and temporally averaged spectra and one-dimensional static models, range from 4 kW/m^2 to 20 kW/m^2. Yet we know that the chromosphere is highly inhomogeneous and dynamic. I shall present work based on SST, ALMA, and IRIS data that, combined with non-LTE and numerical simulations, demonstrates that the chromospheric losses show variations in space and time down to the resolution of the SST. The losses range in magnitude from radiative heating of a few kW/m^2 to cooling of more than 160 kW/m^2. These results provide additional quantitative constraints on models that aim to explain chromospheric heating.