Our team will study chromospheric heating in regions dominated by magnetic activity on the Sun. We will derive time series of semi-empirical 3D models from novel multi-line non-LTE/PRD inversions. These models will be used to study how the different physical parameters change in the photosphere and in the chromosphere as a function of time. These results will be compared with numerical models to identify plausible heating mechanisms. The spectra synthesized from these numerical models will also be used because different heating events/mechanisms can leave unique imprints in the spectral lines and we can use those signatures to further constrain what heating mechanisms are at work. We will focus on the following scientific questions:

1. What heats the chromosphere above plage and active regions? Why do most chromospheric lines show enhanced non-thermal broadening in plage?
2. How does the magnetic field configuration in the photosphere and chromosphere change during flares? How does this relate to changes in other physical parameters? We will study the role of the quiescent pre-flare atmosphere and how it affects the energy deposition during flares using spectropolarimetric observations.
3. What are the dominant heating mechanisms when new magnetic flux emerges into the chromosphere? How does this new flux interact with pre-existing magnetic field?

Expected output: As a results of these meetings, we will make some of our inverted models publicly available. We will start new collaborations that will lead to publications in refereed journals. All papers related to our activities and discussions will acknowledge ISSI’s support.