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The variability of cooling paths in the interstellar gas – Results from joint dynamical and thermal simulations of the interstellar medium
| Speaker: | Dr. Miguel A. de AVILLEZ |
| Affiliation: | Department of Mathematics, University of Évora, Portugal; Zentrum für Astronomie und Astrophysik,Technische Universität Berlin, Germany |
| Date: | June 10, 2015 (Wednesday) |
| Time: | 4:00 p.m. |
| Venue: | Seminar Room 522, 5/F., Chong Yuet Ming Physics Building |
Abstract
The interstellar medium (ISM) is a dynamical system, in which the plasma is naturally driven out of ionization equilibrium due to atomic and dynamic processes operating on different timescales. Consequently, the cooling rates vary as a function of time. Taking into account the dynamics of the plasma, the imbalance becomes even more severe, because adiabatic compression or expansion can change the kinetic temperature of the electrons significantly, while leaving the ionization structure at first unchanged. Hence, ionization and recombination can be delayed, if for example a shock or a rarefaction wave passes over a certain fluid element, respectively.
Detailed numerical studies of the dynamical evolution of the magnetized interstellar medium, including the disk-halo interaction, coupled to a time-dependent follow up of plasma ionization structure have been carried out in order to determine the feedback effect between the dynamics and thermal evolutions of the plasma. The main results of these works are: (i) dependence of the ionization structure on the initial conditions, (ii) the variability of the cooling functions paths for gases with the same initial temperature, but having different evolution histories, and (iii) emission of X-rays at low temperatures due to delayed recombination. A review of these works and their results is presented.
Coffee and tea will be served 20 minutes prior to the seminar.