Influence of energy exchange of electrons and ions on the
  long-wavelength thermal instability in magnetized astrophysical objects
  We investigate thermal instability in an electron-ion magnetized plasma
relevant to galaxy clusters, solar corona, and other two-component
astrophysical objects. We apply the multicomponent plasma approach when the
dynamics of all the species are considered separately through electric field
perturbations. General expressions for perturbations obtained in this paper can
be applied for a wide range of multicomponent astrophysical and laboratory
plasmas also containing the neutrals, dust grains, and other species. We assume
that background temperatures of electrons and ions are different and include
the energy exchange in thermal equations. We take into account the dependence
of collision frequency on density and temperature perturbations. The
cooling-heating functions are taken as different ones for electrons and ions.
As a specific case, we consider a condensation mode of thermal instability of
long-wavelength perturbations when the dynamical time is smaller than a time
during which the particles cover the wavelength along the magnetic field due to
thermal velocity. We derive a general dispersion relation taking into account
the effects mentioned above and obtain simple expressions for growth rates in
limiting cases. Perturbations are shown to have an electromagnetic nature. We
find that at conditions under consideration transverse scale sizes of unstable
perturbations can have a wide spectrum relatively to longitudinal scale sizes
and, in particular, form very thin filaments. The results obtained can be
useful for interpretation of observations of dense cold regions in
astrophysical objects.
