Collisional and viscous damping of MHD waves in partially ionized plasmas of the solar atmosphere

Khodachenko, M. L.; Arber, T. D.; Rücker, H. O.; Hanslmeier, A.

doi:10.1051/0004-6361:20034207

Cited by 127 publications

(157 citation statements)

References 30 publications

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“…The most common form of the MHD theory can only be applied to totally ionized plasma, where the different species are completely coupled dynamically and thermally by collisions, so partial ionization cannot be described. The first extension from MHD in the presence of neutrals for strong collisional coupling is to only consider the modifications due to collisions in the generalized Ohm's law and energy transport (Braginskii 1965;Khodachenko et al 2004;Forteza et al 2007), by assuming a strong thermal coupling and neglecting the transport coefficients. Another way of including partial ionization effects is to use a multi-fluid treatment, where ions and electrons are considered together as an ion-electron fluid (due to their strong electromagnetic coupling) and neutrals are separately considered with as many neutral species as one wishes to include (see, e.g., Zaqarashvili et al 2011b,a;Soler et al 2012a).…”

Section: Fluid Equations For Each Speciesmentioning

confidence: 99%

“…(15) is very difficult. Hence, we first concentrate in the modifications introduced in the ideal MHD theory by the ambipolar term, which has proved to be relevant in solar atmospheric situations (see for example Khodachenko et al 2004;Arber et al 2007;Khomenko & Collados 2012, and references therein). We neglect all the magnetic diffusion terms in this section except the ambipolar one, obtaining a simple form of the induction equation,…”

Section: Mhd and Ambipolar Diffusionmentioning

confidence: 99%

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Rayleigh-Taylor instability in partially ionized compressible plasmas: One fluid approach

Díaz

Khomenko

Collados

2014

A&A

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Aims. We study the modification of the classical criterion for the linear onset and growth rate of the Rayleigh-Taylor instability (RTI) in a partially ionized (PI) plasma in the one-fluid description by considering a generalized induction equation. Methods. The governing linear equations and appropriate boundary conditions, including gravitational terms, are derived and applied to the case of the RTI in a single interface between two partially ionized plasmas. The boundary conditions lead to an equation for the frequencies in which some have positive complex parts, marking the appearance of the RTI. We study the ambipolar term alone first, extending the result to the full induction equation later. Results. The configuration is always unstable because of the presence of a neutral species. In the classical stability regime, the growth rate is small, since the collisions prevent the neutral fluid to fully develop the RTI. For parameters in the classical instability regime, the growth rate is lowered, but the differences with the compressible MHD case are small for the considered theoretical values of the collision frequencies and diffusion coefficients for solar prominences. Conclusions. The PI modifies some aspects of the linear RTI instability, since it takes into account that neutrals do not feel the stabilizing effect of the magnetic field. For the set of parameters representative for solar prominences, our model gives the resulting timescale comparable to observed lifetimes of RTI plumes.

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Section: Fluid Equations For Each Speciesmentioning

confidence: 99%

Section: Mhd and Ambipolar Diffusionmentioning

confidence: 99%

Rayleigh-Taylor instability in partially ionized compressible plasmas: One fluid approach

Díaz

Khomenko

Collados

2014

A&A

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“…with α n a friction coefficient (Braginskii 1965;Khodachenko et al 2004;Leake et al 2005), while the quantity Ξ has been introduced for the reason of compactness of the above linearised equations and its dimensions correspond to the inverse of a friction coefficient. Depending on the value given toμ and to both Spitzer's (η) and Cowling's (η C ) resistivities, we may have different types of plasmas, and those of interest for our study are:…”

Section: Basic and Linearised Equationsmentioning

confidence: 99%

“…In astrophysical plasmas, the typical frequency of MHD waves is much lower than the collisional frequencies between species. In this case, the single fluid approach is usually adopted and has been applied to wave damping in the solar atmosphere (De Pontieu et al 2001;Khodachenko et al 2004;Leake et al 2005). In the case of solar prominences, Forteza et al (2007) derived the full set of MHD equations for a partially ionised, single-fluid plasma and applied them to study the time damping of linear, adiabatic waves in an unbounded prominence medium.…”

Section: Introductionmentioning

confidence: 99%

Time damping of non-adiabatic magnetohydrodynamic waves in a partially ionised prominence medium: Effect of a background flow

Barceló

Carbonell

Ballester

2010

A&A

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Context. The simultaneous occurrence of flows and time damped small-amplitude oscillations in solar prominences is a common phenomenon. These oscillations are mostly interpreted in terms of magnetohydrodynamic (MHD) waves. Aims. We study the time damping of linear non-adiabatic MHD waves in a flowing partially ionised plasma with prominence-like physical conditions. Methods. Considering non-adiabatic single fluid equations for a partially ionised hydrogen plasma, we have solved our dispersion relations for the complex frequency, ω, and we have analysed the behavior of the period, damping time and the ratio of the damping time to the period, versus the real wavenumber k, for Alfvén, fast, slow, and thermal waves. Results. While in the case without flow there is a critical wavenumber at which the period of Alfvén and fast waves goes to infinite, when a flow is present two different critical wavenumbers appear. The smaller wavenumber depends on the flow speed and causes the period of the high-period branch to go to infinite. When the second critical wavenumber is attained the period of both branches become equal. In general, the time damping of Alfvén and fast waves is dominated by resistive effects, and its damping ratio is very inefficient when compared to observations. The damping of slow and thermal waves is basically dominated by non-adiabatic effects, and for slow waves it is possible to obtain a damping ratio close to observations, although it would correspond to long period oscillations with large damping times not often observed. The consideration of a structured medium produces new features such as the apparition of four critical wavenumbers for Alfvén waves, and one critical wavenumber for slow waves. For fast waves, constrained propagation substantially improves, within the range of observed wavelengths, the ratio of the damping time to period. Conclusions. The presence of a background flow in a partially ionised plasma gives place to new interesting features when the time damping of MHD waves is studied. In general, the results point out that ion-neutral collisions are an inefficient mechanism to explain the observed time damping of prominence oscillations if they are produced by Alfvén and fast waves. If the oscillations are produced by slow waves, only long period oscillations with large damping times produce damping ratios in agreement with observations.

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“…In solar physics, there is significant interest in the damping of MHD waves in the solar chromosphere and corona, [1][2][3][4] in the emergence of magnetic flux 5 or in magnetic reconnection. 6,7 In fusion plasmas, models have been developed which are concerned with the influence of the neutral particles in the divertor or edge region of tokamaks.…”

Section: Introductionmentioning

confidence: 99%

Alfvén ionization in an MHD-gas interactions code

Wilson

Diver

2016

Physics of Plasmas

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A numerical model of partially ionized plasmas is developed in order to capture their evolving ionization fractions as a result of Alfvén ionization (AI). The mechanism of, and the parameter regime necessary for, AI is discussed and an expression for the AI rate based on fluid parameters, from a gas-MHD model, is derived. This AI term is added to an existing MHD-gas interactions' code, and the result is a linear, 2D, two-fluid model that includes momentum transfer between charged and neutral species as well as an ionization rate that depends on the velocity fields of both fluids. The dynamics of waves propagating through such a partially ionized plasma are investigated, and it is found that AI has a significant influence on the fluid dynamics as well as both the local and global ionization fraction.

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Collisional and viscous damping of MHD waves in partially ionized plasmas of the solar atmosphere

Cited by 127 publications

References 30 publications

Rayleigh-Taylor instability in partially ionized compressible plasmas: One fluid approach

Rayleigh-Taylor instability in partially ionized compressible plasmas: One fluid approach

Time damping of non-adiabatic magnetohydrodynamic waves in a partially ionised prominence medium: Effect of a background flow

Alfvén ionization in an MHD-gas interactions code

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