Robert J. Rutten (Lingezicht Astrophysics & Institute for Theoretical Astrophysics Oslo)
The chromosphere is the interface between the photospheric solar surface and the outer corona and wind. In this complex domain the solar gas becomes transparent throughout the ultraviolet and in the strongest spectral lines while magnetic pressure becomes dominant over gas pressure even in weak-field regions. Fine-scale magnetically caused or guided dynamic processes in the chromosphere constitute the roots of mass and energy loading of the corona and solar wind. Notwithstanding this pivotal role the chromosphere remained ill-understood after its basic NLTE radiation physics was formulated in the 1960s and 70s. Presently, both chromospheric observation and chromospheric simulation mature towards the required sophistication. The open-field features seem of greater interest than the easier-to-see closed-field features. For the latter, the grail of coronal topology and eruption prediction comes in sight.
I will start with an introductory overview, show movies to present the state of art in observation and simulation, and treat some recent success stories in more detail.