| Presentation Title: | Beyond density diagnostics: combining O IV 1399, 1401, Si IV |
| Author(s): | Juan Martinez-Sykora, Paola Testa, Vanessa Polito, Bart De Pontieu |
Abstract:
Previous studies revealed the complexity of using Si IV and O IV as diagnostics when considering non-equilibrium ionization (NEQ). For this research, we combine IRIS, EIS observations, and 2.5D radiative MHD models where the oxygen and silicon ionization are computed in non-equilibrium ionization and compare them to the case assuming statistical equilibrium (SE). We use these results to provide new insights into interpreting O IV and SI IV observations of an active region with IRIS, including the nature of the transition region emission. The NEQ effects lead to a similar column depth for all the transitions. The O IV 1399 and 1401 ratio can provide the column depth, which can used to calculate the density from the Si IV intensity. We also analyze column depth properties. The differences may provide transition region abundance diagnostics using IRIS, and we aim to compare these abundances derived from IRIS with those derived from Hinode/EIS data at higher temperatures.