The heating of the Sun's chromosphere remains poorly understood. While
progress has been made on understanding what drives the quiet Sun internetwork
chromosphere, chromospheric heating in strong magnetic field regions continues
to present a difficult challenge, mostly because of a lack of observational
constraints. We use high-resolution spectropolarimetric data from the Swedish
1-m Solar Telescope to identify the location and spatio-temporal properties of
heating in the magnetic chromosphere. In particular, we report the existence of
raised-core spectral line profiles in the Ca II 8542 line. These profiles are
characterized by the absence of an absorption line core, showing a quasi-flat
profile between +/- 0.5 {\AA}, and are abundant close to magnetic bright-points
and plage. Comparison with 3D MHD simulations indicates that such profiles
occur when the line-of-sight goes through an "elevated temperature canopy"
associated with the expansion with height of the magnetic field of flux
concentrations. This temperature canopy in the simulations is caused by ohmic
dissipation where there are strong magnetic field gradients. The raised-core
profiles are thus indicators of locations of increased chromospheric heating.
We characterize the location and temporal and spatial properties of such
profiles in our observations, thus providing much stricter constraints on
theoretical models of chromospheric heating mechanisms than before.Comment: Accepted for publication in ApJ
