J/A+A/616/A58 Variability of the adiabatic parameter (de Avillez+, 2018)
Variability of the adiabatic parameter in monoatomic thermal and non-thermal
plasmas.
de Avillez M.A., Anela G.J., Breitschwerdt D.
<Astron. Astrophys. 616, A58 (2018)>
=2018A&A...616A..58D 2018A&A...616A..58D (SIMBAD/NED BibCode)
ADC_Keywords: Energy distributions ; Atomic physics ; Models
Keywords: atomic processes - atomic data - hydrodynamics - methods: numerical -
ISM: general - intergalactic: medium
Abstract:
Numerical models of the evolution of interstellar and intergalactic
plasmas often assume that the adiabatic parameter γ (the ratio
of the specific heats) is constant (5/3 in monoatomic plasmas).
However, γ is determined by the total internal energy of the
plasma, which depends on the ionic and excitation state of the plasma.
Hence, the adiabatic parameter may not be constant across the range of
temperatures available in the interstellar medium. We aim to carry out
detailed simulations of the thermal evolution of plasmas with
Maxwell-Boltzmann and non-thermal (κ and n) electron
distributions in order to determine the temperature variability of the
total internal energy and of the adiabatic parameter. The plasma,
composed of H, He, C, N, O, Ne, Mg, Si, S, and Fe atoms and ions,
evolves under collisional ionization equilibrium conditions, from an
initial temperature of 109K. The calculations include electron
impact ionization, radiative and dielectronic recombinations and line
excitation. The ionization structure was calculated solving a system
of 112 linear equations using the Gauss elimination method with scaled
partial pivoting. Numerical integrations used in the calculation of
ionization and excitation rates are carried out using the
double-exponential over a semi-finite interval method. In both methods
a precision of 10-15 is adopted. The total internal energy of the
plasma is mainly dominated by the ionization energy for temperatures
lower than 8x104K with the excitation energy having a contribution
of less than one percent. In thermal and non-thermal plasmas composed
of H, He, and metals, the adiabatic parameter evolution is determined
by the H and He ionizations leading to a profile in general having
three transitions. However, for κ distributed plasmas these
three transitions are not observed for {kappa<15} and for {kappa<5}
there are no transitions. In general, γ varies from 1.01 to 5/3.
Lookup tables of the γ parameter are presented as supplementary
material.
Description:
Tables 1 and 2 present the adiabatic parameter of the gas versus
temperature (K) for the Maxwellian, n and κ distributions,
with n, kappa = 2, 3, 5, 10 and 15.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 600 gamma vs. logT for MB and kappa distributions
table2.dat 76 600 gamma vs. logT for MB and n distributions
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Byte-by-byte Description of file:table1.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 [K] logT Temperature in log scale
7- 16 E10.5 --- MB gamma for MB distribution
19- 28 E10.5 --- k2 gamma for k=2 distribution
31- 40 E10.5 --- k3 gamma for k=3 distribution
43- 52 E10.5 --- k5 gamma for k=5 distribution
55- 64 E10.5 --- k10 gamma for k=10 distribution
67- 76 E10.5 --- k15 gamma for k=15 distribution
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 [K] logT Temperature in log scale
7- 16 E10.4 --- n1 gamma for n=1 distribution (MB distribution)
19- 28 E10.4 --- n2 gamma for n=2 distribution
31- 40 E10.4 --- n3 gamma for n=3 distribution
43- 52 E10.4 --- n5 gamma for n=5 distribution
55- 64 E10.4 --- n10 gamma for n=10 distribution
67- 76 E10.4 --- n15 gamma for n=15 distribution
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Acknowledgements:
Miguel A. de Avillez, mavillez(at)galaxy.lca.uevora.pt
(End) M.A. de Avillez [UEvora, Portugal], P. Vannier [CDS] 19-May-2018