Non-equilibrium hydrogen ionization in 3D simulations of the solar chromosphere

The assumption of statistical equilibrium for atomic level populations does not hold under the conditions of the dynamic chromosphere. In order to calculate the hydrogen ionization balance and the electron density one has to solve the time-dependent rate equations. I will present results from 2D and 3D chromospheric simulations incorporating the time-dependent rate equations for hydrogen. Both the hydrogen ionization degree and the electron density in our model chromosphere are much more constant over position and time than LTE and equilibrium non-LTE theory predict. These simulations provide multi-dimensional model atmospheres with realistic electron densities that can be used in detailed radiative transfer modelling.