SOLARNET Conference: The Many Scales of the Magnetic Sun

Understanding the physical processes in the solar chromosphere requires comprehensive models which can be compared to observations. These models include the treatment of magnetic fields, heat conduction and radiative transfer (RT). However, usually models fail to reproduce observed properties of chromospheric spectral lines. The MgII h&k lines form in the middle to upper chromosphere and are observed by the IRIS satellite mission with high precision. The forward modeled spectral lines appear on average to have too narrow line widths and larger peak asymmetries than the observations.
We use the recently developed chromospheric extension of the radiative MHD code MURaM to simulate an enhanced network (EN) region. From the resulting modeled atmospheres we use the RT codes RH1.5D and Multi3D to synthesize the MgII h&k lines in 1D and 3D RT. We find that the line width as well as the peak separations from the forward modeled spectra are on average larger and in better agreement to observations. We discuss the physical properties such as velocity gradients and density stratification in the chromosphere of the modeled atmosphere that lead to the improved synthetic spectral profiles.