The first adiabatic exponent in a partially ionized prominence plasma: Effect on the period of slow waves

Ballester, J. L.; Soler, Roberto; Carbonell, M.; Terradas, J.

doi:10.1051/0004-6361/202141851

Cited by 10 publications

(7 citation statements)

References 34 publications

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“…It is noted that the filament plasma in our simulations was considered to be fully ionized for simplicity. In real situations the temperature of the filament plasma is ∼7000 K, where partial ionization and optically thick radiation begin to take effect for internal waves propagating inside the filament (Ballester et al 2018(Ballester et al , 2020(Ballester et al , 2021. For the global pendulum mode oscillations studied in this paper, these internal waves are not directly involved.…”

Section: Discussionmentioning

confidence: 92%

Decayless longitudinal oscillations of a solar filament maintained by quasi-periodic jets

Guo

Zhang

et al. 2022

A&A

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Context. As a ubiquitous phenomenon, large-amplitude longitudinal filament oscillations usually decay in 1–4 periods. Recently, we observed a decayless case of such oscillations in the corona. Aims. We try to understand the physical process that maintains the decayless oscillation of the filament. Methods. Multiwavelength imaging observations and magnetograms were collected to study the dynamics of the filament oscillation and its associated phenomena. To explain the decayless oscillations, we also performed one-dimensional hydrodynamic numerical simulations using the code MPI-AMRVAC. Results. In observations, the filament oscillates without decay with a period of 36.4 ± 0.3 min for almost 4 h before eruption. During oscillations, four quasi-periodic jets emanate from a magnetic cancellation site near the filament. The time interval between neighboring jets is ∼68.9 ± 1.0 min. Numerical simulations constrained by the observations reproduced the decayless longitudinal oscillations. However, it is surprising to find that the period of the decayless oscillations is not consistent with the pendulum model. Conclusions. We propose that the decayless longitudinal oscillations of the filament are maintained by quasi-periodic jets, which is verified by the hydrodynamic simulations. More importantly, it is found that, when it is driven by quasi-periodic jets, the period of the filament longitudinal oscillations also depends on the driving period of the jets, not on the pendulum period alone. With a parameter survey in simulations, we derived a formula by which the pendulum oscillation period can be derived using the observed period of decayless filament oscillations and the driving periods of jets.

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Section: Discussionmentioning

confidence: 92%

Decayless longitudinal oscillations of a solar filament maintained by quasi-periodic jets

Guo

Zhang

et al. 2022

A&A

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“…Assuming a radiative loss function, along with numerical values for a and γ, one obtains a numerical value for b that satisfies Equation ( 32): for instance, taking a = 2, γ = 5/3 and α = 7.4 [42] from Equation (32), one obtains b = 5.9. Another possibility is that, with assumed numerical values for b and γ, the value of a can be determined, satisfying Equation (33). Figure 7 (left) displays the behavior of thermal misbalance times versus the b exponent.…”

Section: Resultsmentioning

confidence: 99%

“…The assumed heating mechanisms were density-and temperature-dependent, and it was shown that for some dependences, slow waves could be amplified. Furthermore, the effect of the temperatureand ionization-degree-dependence of the adiabatic coefficient, γ, in a partially ionized hydrogen plasma [33] was also considered. However, in the dispersion relation obtained from the linear analysis, and when parallel propagation was considered, ambipolar diffusion only influenced Alfvén waves, but not slow waves, which were only affected by radiative losses and heating; therefore, these thermal mechanisms became responsible for the damping/amplification of the oscillations.…”

Section: Introductionmentioning

confidence: 99%

“…[20], are introduced to the present study: first, apart from ambipolar diffusion, the case of thermal misbalance is considered, and the temporal behavior of slow magnetoacoustic waves is studied, paying attention to the damping/amplification of these waves; second, due to the uncertainty of prominence heating, the calculations consider a general heating term such as H = hρ a T b , taking a and b as free parameters; third, the thermodynamics of partially ionized gas [41] differ from those of fully ionized or fully neutral gas, and the consideration of a constant value for the adiabatic coefficient, γ, would overestimate the gas temperature [33]; therefore, in this study three different cases are considered. Initially, and for comparison, a constant γ = 5/3 is considered; then, the first adiabatic exponent, Γ 1 , is computed under non-local thermodynamic equilibrium (NLTE) and local thermodynamic equilibrium (LTE) conditions [33], whose numerical values depend on density, temperature and ionization degree. Furthermore, a comparison between Hildner [42] and CHIANTI7 [43][44][45] radiative functions was also included.…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear Coupling of Alfvén and Slow Magnetoacoustic Waves in Partially Ionized Solar Plasmas: The Effect of Thermal Misbalance

Ballester¹

2023

Physics

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Solar chromosphere and photosphere, as well as solar atmospheric structures, such as prominences and spicules, are made of partially ionized plasmas. Observations have reported the presence of damped or amplified oscillations in these solar plasmas, which have been interpreted in terms of magnetohydrodynamic (MHD) waves. Slow magnetoacoustic waves could be responsible for these oscillations. The present study investigates the temporal behavior of the field-aligned motions that represent slow magnetoacoustic waves excited in a partially ionized prominence plasma by the ponderomotive force. Starting from single-fluid MHD equations, including radiative losses, a heating mechanism and ambipolar diffusion, and using a regular perturbation method, first- and second-order partial differential equations have been derived. By numerically solving second-order equations describing field-aligned motions, the temporal behavior of the longitudinal velocity perturbations is obtained. The damping or amplification of these perturbations can be explained in terms of heating–cooling misbalance, the damping effect due to ambipolar diffusion and the variation of the first adiabatic exponent with temperature and ionization degree.

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“…with being the hydrogen-ionization potential. From this expression it can be seen that for a fully ionized or fully neutral hydrogen plasma γ = 5/3, while for temperatures around 6000 K the adiabatic exponent reaches a minimum value of about 1.1 (Ballester et al, 2021). Then, once the ionization degree is known, from Equation 77the new value for γ can be determined.…”

Section: Qualitative Descriptionmentioning

confidence: 98%

The Effect of Thermal Misbalance on Slow Magnetoacoustic Waves in a Partially Ionized Prominence-Like Plasma

Ibanez¹,

Ballester²

2022

Sol Phys

Self Cite

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Solar prominences are partially ionized plasma structures embedded in the solar corona. Ground- and space-based observations have confirmed the presence of oscillatory motions in prominences, which have been interpreted in terms of standing or propagating MHD waves. Some of these observations suggest that slow magnetoacoustic waves could be responsible for these oscillations and have provided us with evidence about their damping/amplification with very small ratios between damping/amplifying times and periods, which have been difficult to explain from a theoretical point of view. Here we investigate the temporal behavior of non-adiabatic, slow, magnetoacoustic waves when a heating–cooling misbalance is present. The influence of optically thin losses and of a general heating term, in which density and temperature dependence can be modified, as well as the effect of partial ionization have been considered. Furthermore, a tentative example of how, using observational data, the observed ratio between damping/amplifying times and periods could be matched with those theoretically obtained is shown. In summary, different combinations of radiative losses, heating mechanisms, and typical wavenumbers, together with the effect of partial ionization, could provide a theoretical tool able to reproduce observational results on small-amplitude oscillations in prominences.

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The first adiabatic exponent in a partially ionized prominence plasma: Effect on the period of slow waves

Cited by 10 publications

References 34 publications

Decayless longitudinal oscillations of a solar filament maintained by quasi-periodic jets

Decayless longitudinal oscillations of a solar filament maintained by quasi-periodic jets

Nonlinear Coupling of Alfvén and Slow Magnetoacoustic Waves in Partially Ionized Solar Plasmas: The Effect of Thermal Misbalance

The Effect of Thermal Misbalance on Slow Magnetoacoustic Waves in a Partially Ionized Prominence-Like Plasma

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