Recent Results in Chromospheric Studies

The solar chromosphere is a challenging and complex plasma environment, in which many of the observed phenomena and physical processes have not yet been fully understood. Our knowledge has seen improvements in the last decade due to enhanced observational coverage from space-based missions like Hinode, SDO and IRIS, novel rocket experiments such as Sunrise and CLASP, and significant contributions from ground-based observatories like GREGOR, GST, SST, and ALMA. Improved numerical modeling capabilities have been developed to include a more complete and realistic treatment of the radiative transfer processes, non-thermal energy deposition, and the polarization effect of magnetic fields in spectral line emission. Significant efforts have focused on explaining the observed dynamics and emission of the plasma with assumptions about the behavior of the magnetic field and have contributed to improving models and identifying gaps in our knowledge. The few measurements of the magnetic field permeating the chromosphere have provided important clues to understanding the processes at play. In the absence of routine measurements we are left seeing only the consequences imposed by the magnetic field on emitting plasma and guessing at the reason for the observed dynamics. While upcoming DKIST high resolution observations will address some key aspects of chromospheric phenomena, the development of instrumentation focused on field-sensitive lines in novel spectral regions would provide new insights into this fascinatingly complex layer of the solar atmosphere.