The ionization structure of interstellar plasmas evolving with non-thermal electrons

Speaker: Prof. Miguel A. de Avillez, Department of Mathematics, University of Evora, Portugal

Abstract:

Many models of the ISM or isolated phenomena, such as bubbles, superbubbles, etc.,
take for granted that the gas is not only in thermal equilibrium, but also in the so-called
collisional ionization equilibrium (CIE). However, cooling and heating may not be synchronized
with recombination and ionization, respectively. Thus, the system is in the so called
non-equilibrium ionization. Furthermore, there is ample evidence that thermal equilibrium may
not be the exclusive situation in the ISM. Thus, electrons may well be described by distributions
other than Maxwellian, e.g. kappa- or n-distributions. Plasma emission analysis in Astrophysics
using different codes and databases often assumes a Maxwellian distribution for the electrons.
But if a kappa- or n-distribution is considered one has to carry out a full blown recalculation
of all the rates (ionization, recombination, charge exchange, excitation) as well as the thermally
averaged and total Gaunt factors associated with the processes contributing for the continuum
and line emission. The latter through the excitation and deexcitation rates. Here, a review of
these matters is carried out.