| Name | Anusha Lokanathapura S Bhasari |
| Affiliation | Max Planck Institute for Solar System Research |
| Title | Non-equilibrium equation-of-state for the solar atmosphere |
| Authors | Anusha L. S., M. van Noort and R. Cameron |
| Abstract | In the solar chromospheres, radiative energy transport is dominated by only the strongest spectral lines. For these lines, the approximation of local-thermodynamic-equilibrium (LTE) is known to be very inaccurate, and a state of equilibrium cannot be assumed in general. To calculate the radiative energy transport under these conditions, the population evolution equation must be evaluated explicitly, including all time dependent terms. In this talk I present a numerical method that we developed recently to solve the evolution equation for the atomic level populations in a time-implicit way, keeping all time dependent terms to first order. We solve the non-LTE non-equilibrium radiative transfer (RT) problem through a proper time-dependent treatment of the radiation field and non-equilibrium treatment of the atoms and hydrogen molecules. The method is based on an integral equation approach to the RT equation that involves a generalization to the time dimension, of i) the short-characteristic technique for the formal solution of the RT equation and the ii) Multi-level Approximate Lambda Iteration technique to solve the non-linear rate system. We validate our newly developed method with two important benchmark tests: i) we start with LTE populations on a fixed atmospheric structure, allow them to evolve to the equilibrium solution, and verify that this agrees with the kinetic equilibrium solution obtained from the RH code of Uitenbroek (2001), ii) we show that the physical time-scales required to reach equilibrium are similar to those obtained by Carlsson & Stein (2002) who use a different numerical method. We also showed that the solver remains stable and the solution is robust against changes in the time resolution. |
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