Constraining magnetic heating in the solar chromosphere

Abstract: The chromospheric and coronal heating problems remain one of the foremost open questions in solar and stellar physics: how are the outer layers of the Sun heated from a few thousand kelvin in the photosphere to the million-degree corona? Radiation alone is not capable of transporting the required energy to explain observations from the inner layers. Phenomena associated with the presence of magnetic fields could provide the missing energy. However, the reconstruction of the magnetic field vector from observations is complex because radiation must be modelled under non-local thermodynamical equilibrium conditions. Additionally, it is hard to achieve high spatio-temporal cadence and a sufficiently high signal-to-noise ratio simultaneously. Therefore, observational datasets are greatly affected by noise. The aim of this thesis was to improve the fidelity of an efficient technique to derive the magnetic field vector (a spatially-constrained weak-field approximation in Paper I), to derive the full stratification of the magnetic field in plage regions, and to study the chromospheric radiative losses and their relation to the magnetic field stratification. By studying the spatio-temporal distribution of the radiative losses in Paper II, we could discern the constribution from some heating mechanisms in the chromosphere from an observational perspective. In Paper III, we study the magnetic field strength of low-lying chromospheric loops in order to set constraints on the heating mechanisms that could be at work in these structures.