Turbulence is a fundamental process that drives
mixing and energy redistribution across a wide
range of astrophysical systems. For warm (T ≈ 104 K)
plasma, the material is partially ionized, consisting
of both ionized and neutral species. The interactions
between ionized and neutral species are thought to
play a key role in heating ...
Turbulence is a fundamental process that drives
mixing and energy redistribution across a wide
range of astrophysical systems. For warm (T ≈ 104 K)
plasma, the material is partially ionized, consisting
of both ionized and neutral species. The interactions
between ionized and neutral species are thought to
play a key role in heating (or cooling) of partially
ionized plasmas. Here, mixing is studied in a two fluid partially ionized plasma undergoing the shear driven Kelvin–Helmholtz instability to evaluate the
thermal processes within the mixing layer. Two dimensional numerical simulations are performed
using the open-source (PIP) code that solves for a two fluid plasma consisting of a charge-neutral plasma
and multiple excited states of neutral hydrogen. Both
collisional and radiative ionization and recombination
are included. In the mixing layer, a complex array of
ionization and recombination processes occur as the
cooler layer joins the hotter layer, and vice versa. In
localized areas of the mixing layer, the temperature
exceeds the initial temperatures of either layer with
heating dominated by collisional recombinations
over turbulent dissipation. The mixing layer is in
approximate ionization-recombination equilibrium,
however the obtained equilibrium is different to
the Saha–Boltzmann local thermal equilibrium. The
dynamic mixing processes may be important in
determining the ionization states, and with that
intensities of spectral lines, of observed mixing layers.
This article is part of the theme issue ‘Partially
ionized plasma of the solar atmosphere: recent
advances and future pathways’