Issue |
A&A
Volume 656, December 2021
|
|
---|---|---|
Article Number | A159 | |
Number of page(s) | 10 | |
Section | The Sun and the Heliosphere | |
DOI | https://doi.org/10.1051/0004-6361/202141851 | |
Published online | 16 December 2021 |
The first adiabatic exponent in a partially ionized prominence plasma: Effect on the period of slow waves
1
Departament de Física, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain
e-mail: joseluis.ballester@uib.es
2
Departament de Ciències Matemàtiques i Informàtica, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain
3
Institute of Applied Computing & Community Code (IAC3), Universitat de les Illes Balears, Spain
Received:
23
July
2021
Accepted:
4
October
2021
Partially ionized plasmas are found in many different astrophysical environments. The study of partially ionized plasmas is of great interest for solar physics because some layers of the solar atmosphere (photosphere and chromosphere) as well as solar structures, such as spicules and prominences, are made of these kinds of plasmas. To our knowledge, despite it being known that the adiabatic coefficient, γ, or the first adiabatic exponent, Γ1, depend on the ionization degree, this fact has been disregarded in all the studies related to magnetohydrodynamic waves in solar partially ionized plasmas. However, in other astrophysical areas, the dependence of γ or Γ1 on the plasma ionization degree has been taken into account. Therefore, our aim here is to study how, in a plasma with prominence physical properties, the joint action of the temperature, density, and ionization degree modifies the numerical values of the first adiabatic exponent Γ1 which affects the adiabatic sound speed and the period of slow waves. In our computations, we have used two different approaches; first of all, we assume local thermodynamic equilibrium (LTE) and, later, we consider a non-local thermodynamic equilibrium (non-LTE) model. When comparing the results in the LTE and non-LTE cases, the numerical values of Γ1 are clearly different for both and they are probably strongly dependent on the assumed model which determines how the ionization degree evolves with temperature. Finally, the effect of the ionization degree dependence of Γ1 on the period of slow waves has been determined showing that it can be of great importance for seismological studies of partially ionized solar structures.
Key words: magnetohydrodynamics (MHD) / Sun: filaments / prominences / Sun: oscillations
© J. L. Ballester et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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