89 research outputs found
Electrical conductivity of plasmas of DB white dwarf atmospheres
The static electrical conductivity of non-ideal, dense, partially ionized
helium plasma was calculated over a wide range of plasma parameters:
temperatures and mass density . Calculations of
electrical conductivity of plasma for the considered range of plasma parameters
are of interest for DB white dwarf atmospheres with effective temperatures
.
Electrical conductivity of plasma was calculated by using the modified random
phase approximation and semiclassical method, adapted for the case of dense,
partially ionized plasma. The results were compared with the unique existing
experimental data, including the results related to the region of dense
plasmas. In spite of low accuracy of the experimental data, the existing
agreement with them indicates that results obtained in this paper are correct
Modeling of the Continuous Absorption of Electromagnetic Radiation in Dense Hydrogen Plasma
In this work is examined a new modeling way of describing the continuous
absorption of electromagnetic (EM) radiation in a dense partially ionized
hydrogen plasmas with electron densities about cm -
cm and temperatures about K - K in the wavelength region . The obtained results can be applied to the plasmas of the
partially ionized layers of different stellar atmospheres
The ion-atom absorption processes as one of the factors of the influence on the sunspot opacity
As a continuation of the previous investigations of the symmetric and
strongly non-symmetric ion-atom absorption processes in the far UV region
within the models of the quiet Sun photosphere, these processes are studied
here within a model of the sunspot. Here we mean the absorption processes in
the H+H and H collisions and the processes of the
photo-dissociation of the H and H molecular ions, where is
one of the metal atoms: Na, Ca, Mg, Si and Al. Obtained results show that
the influence of the considered ion-atom absorption processes on the opacity of
sunspots in the considered spectral region (110 nm
230 nm) is not less and in some parts even larger than the influence of the
referent electron-atom processes. In such a way, it is shown that the
considered ion-atom absorption processes should be included \emph{ab initio} in
the corresponding models of sunspots of solar-type and near solar-type stars.
Apart of that, the spectral characteristics of the considered non-symmetric
ion-atom absorption processes (including here the case = Li), which can be
used in some further applications, have been determined and presented within
this work.Comment: Accepted in Monthly Notices of the Royal Astronomical Societ
Excitation and deexcitation processes in atom-Rydberg atom collisions in helium-rich white dwarf atmospheres
We aim to show the importance of non-elastic excitation and deexcitation
processes in collisions with the
principal quantum number for helium-rich white dwarf atmospheres. We
compare the efficiencies of these processes with those of the known non-elastic
electron- atom processes in the atmospheres of some DB
white dwarfs. We show that in significant parts of the considered atmospheres,
which contain weakly ionized layers (the ionization degree ),
the influence of the studied atom-Rydberg atom processes on excited helium atom
populations is dominant or at least comparable to the influence of the
concurrent electron--atom processes.Comment: Astronomy & Astrophysics, Accepted: 14 February 201
The influence of the radiative non-symmetric ion-atom collisions on the stellar atmospheres in VUV region
The aim of this work is to draw attention to the processes of radiative
charge exchange in non-symmetric ion-atom collisions as a factor of influence
on the opacity of stellar atmospheres in VUV region. For that purpose
calculations of the spectral absorption coefficients for several ion-atom
systems, namely: He + H and H + X, where X = Na and Li have been
performed. On chosen examples it has been established that the examined
processes generate rather wide molecular absorption bands in the VUV region,
which should be taken into account for the interpretation of data obtained from
laboratory measurements or astrophysical observations. In this paper the
potential significance is discussed of the considered radiative processes for
DB white dwarfs and solar atmospheres, as well as for the atmospheres of the
so-called lithium stars
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