[e.g. @2012ApJ...750...51K] as well as techniques to constrain extrapolation of the magnetic field from photospheric magnetograms [e.g. @2016ApJ...826...61A].]{}

[Another prominent feature in the chromosphere during the flaring phase in active regions, are *flare ribbons*.]{} [According to the standard flare model [@2008LRSP....5....1B; @2011SSRv..159...19F], these are locations where energy is deposited in the chromosphere predominantly by beams of energetic electrons precipitating down from the coronal reconnection site.]{} [Strong chromospheric lines typically show broad emission peaks at those locations which models have difficulty to reproduce.]{}

[The main problem in modeling both long fibrils and flare ribbons is that the radiation originating from the solar chromosphere forms under complex non-Local Thermodynamic Equilibrium (non-LTE) conditions.]{} [On the one hand, this makes observations of the chromosphere difficult to interpret; on the other hand, the forward synthesis of chromospheric lines becomes quite complex and computationally expensive if one wants to reproduce the spectral lines in detail. ]{}

[The backbone of theoretical studies of 3D line formation in the solar chromosphere was so far the “enhanced network” run computed with the 3D radiation-MHD code Bifrost .]{} [A simulation including flux emergence performed with the same code has also been used [@2017ApJ...839...22H].]{}

[In case of flares, modeling of chromospheric 