Abstract
Due to long recombination and ionization times, ions passing through the transition region potentially do not have time to adjust their ionization state to the local temperature. As a result we can find low temperature ions in high temperature regions or vice vera. The dynamical timescales of the chromosphere and transition region are faster then the typical equilibration times of ions, and spectroscopic investigations will therefore not give correct information on local quantities. We investigate the severity of this problem with the help of numerical modelling.
Modeling of the ionization equilibrium have previously been done i 1D, but because of the many free parameters in these models, their conclusions are not free of uncertainties. With the recent solar atmosphere model Bifrost, we have a 3D platform for calculating and following the ionization degree of important atoms of high abundances in the solar atmosphere. We will here give a presentation of the preliminary results of this work.