摘要：Context.The radiative losses in the solar chromosphere vary from 4 kW m−2in the quiet Sun, to 20 kW m−2in active regions. The mechanisms that transport non-thermal energy to and deposit it in the chromosphere are still not understood.Aim.We aim to investigate the atmospheric structure and heating of the solar chromosphere in an emerging flux region.Methods.We have used observations taken with the CHROMIS and CRISP instruments on the Swedish 1-m Solar Telescope in the CaIIK , CaII854.2 nm, Hα, and FeI630.1 nm and 630.2 nm lines. We analysed the various line profiles and in addition perform multi-line, multi-species, non-local thermodynamic equilibrium (non-LTE) inversions to estimate the spatial and temporal variation of the chromospheric structure.Results.We investigate which spectral features of CaIIK contribute to the frequency-integrated CaIIK brightness, which we use as a tracer of chromospheric radiative losses. The majority of the radiative losses are not associated with localised high-CaIIK-brightness events, but instead with a more gentle, spatially extended, and persistent heating. The frequency-integrated CaIIK brightness correlates strongly with the total linear polarization in the CaII854.2 nm, while the CaIIK profile shapes indicate that the bulk of the radiative losses occur in the lower chromosphere. Non-LTE inversions indicate a transition from heating concentrated around photospheric magnetic elements below logτ500= −3 to a more space-filling and time-persistent heating above logτ500= −4. The inferred gas temperature at logτ500= −3.8 correlates strongly with the total linear polarization in the CaII854.2 nm line, suggesting that that the heating rate correlates with the strength of the horizontal magnetic field in the low chromosphere.
关键词：Key wordsenSun: atmosphereSun: chromosphereSun: magnetic fields
