A model for quiescent solar prominences

Milne, A. M.; Priest, E. R.; Roberts, Benjamin W.

doi:10.1086/157290

Cited by 49 publications

(32 citation statements)

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“…The use of an optically thin plasma radiative cooling seems to be a reasonable approach for coronal, or almost coronal, conditions, while it may not be valid for prominence conditions because they are optically thick. In this case, the radiative losses from the internal part of the prominence are greatly reduced and this can be represented by changing the exponent α in the cooling function, for temperatures T ≤ 10 4 K, from α = 7.4 to 17.4 (Milne et al 1979) or α = 30 (Rosner et al 1978), as well as by changing χ * accordingly. Finally, the last term in Eq.…”

Section: Basic Equationsmentioning

confidence: 99%

“…κ is the mean free path of the conducting particles, while k ρ and k T are the wavenumbers of sound waves whose angular frequencies are numerically equal to the growth rates 17.4 0.8 Milne et al (1979) Prominence ( (1974) of isothermal and isochoric perturbations, respectively; in the presence of a magnetic field, k T corresponds to k T modified by conduction effects. Using these quantities and the above expressions of A and H, we obtain…”

Section: Basic Equationsmentioning

confidence: 99%

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Time damping of linear non-adiabatic magnetohydrodynamic waves in an unbounded plasma with solar coronal properties

Carbonell

Oliver²,

Ballester³

2004

A&A

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Abstract.In this paper, we study the time damping of magnetoacoustic waves when the adiabaticity assumption is removed by means of an energy equation which includes optically thin radiative losses, thermal conduction and heating. For the sake of simplicity, this study has been done for a homogeneous, isothermal and unbounded medium permeated by a uniform magnetic field, with physical properties akin to those of the corona, the prominence-corona transition region (PCTR) and prominences. In some PCTR regimes and in the coronal regime wave instabilities appear, which prevents the computation of the damping time and the damping per period for part of the wavenumber interval considered. Furthermore, except for one of the PCTR regimes, in the rest of the regimes the apparition of those instabilities depends on the heating mechanism considered. Also, for the same heating mechanism, the behaviour of the damping time for the different considered regimes changes significantly when going from very small to very large wavenumbers and, in all the regimes, it becomes almost constant for very large wavenumbers.

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Section: Basic Equationsmentioning

confidence: 99%

Section: Basic Equationsmentioning

confidence: 99%

Time damping of linear non-adiabatic magnetohydrodynamic waves in an unbounded plasma with solar coronal properties

Carbonell

Oliver²,

Ballester³

2004

A&A

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“…Owing to finite optical thickness, the actual radiative losses of the plasma would be reduced in comparison to the optically thin case, so that the thermal mode growth rate would decrease consistently (see Carbonell et al 2006). Some attempts to incorporate the effect of finite optical thickness in Hildner's parametrization can be found in, e.g., Rosner et al (1978) and Milne et al (1979). To our knowledge, the effect of finite optical thickness has not been incorporated in more up-to-date loss functions.…”

Section: Discussionmentioning

confidence: 99%

Stability of thermal modes in cool prominence plasmas

Soler

Ballester

Parenti

2012

A&A

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Magnetohydrodynamic thermal modes may play an important role in the formation, plasma condensation, and evolution of solar prominences. Unstable thermal modes due to unbalance between radiative losses and heating can lead to rapid plasma cooling and condensation. An accurate description of the radiative loss function is therefore crucial for this process. We study the stability of thermal modes in unbounded and uniform plasmas with properties akin to those in solar prominences. Effects of partial ionization are taken into account. Three different parametrizations of the radiative loss function are used. By means of a normal mode analysis, we investigate linear nonadiabatic perturbations superimposed on the equilibrium state. We find an approximate instability criterion for thermal modes, while the exact linear growth rate is obtained by numerically solving the general dispersion relation. The stability of thermal disturbances is compared for the three different loss functions that we consider. Using up-to-date computations of radiative losses derived from the CHIANTI atomic database, we find that thermal modes may be unstable in prominences for lower temperatures than those predicted with previously existing loss functions. Thermal instability can take place for temperatures as low as about 15 000 K. The obtained linear growth rates indicate that this instability might have a strong impact on the dynamics and evolution of cool prominence condensations.

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“…The use of an optically thin plasma radiative cooling seems to be a reasonable approach for coronal, or almost coronal, conditions, while it may not be valid for prominence conditions because they are optically thick in some spectral lines. In this case, the radiative losses from the internal part of the prominence are greatly reduced and this can be represented by changing the exponent α in the cooling function, for temperatures T ≤ 10 4 K, from α = 7.4 to 17.4 (Milne et al 1979) or α = 30 (Rosner et al 1978), as well as by changing χ * accordingly. Finally, the last term in Eq.…”

Section: Basic Equationsmentioning

confidence: 99%

Spatial damping of linear non-adiabatic magnetoacoustic waves in a prominence medium

Carbonell¹,

Terradas

Oliver

et al. 2006

A&A

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Aims. We study the spatial damping of linear non-adiabatic magnetoacoustic waves in a homogeneous, isothermal, and unbounded medium permeated by a uniform magnetic field, with physical properties akin to those of solar prominences. Methods. We consider an energy equation with optically thin radiative losses, thermal conduction, and heating, and linearize the MHD equations to obtain a sixth-order polynomial in the wavenumber k, which represents the dispersion relation for slow, fast, and thermal MHD waves. Since we are interested in the spatial damping, we have taken ω as real and have numerically solved the dispersion relation to obtain complex solutions for the wavenumber k corresponding to fast, slow, and thermal waves.Results. The thermal wave shows the strongest spatial damping, while the fast wave shows the weakest spatial damping. At periods greater than 1 s the spatial damping of magnetoacoustic waves is dominated by radiation, while at shorter periods the spatial damping is dominated by thermal conduction. For very short periods the isothermal regime is attained and the damping length becomes almost constant. Conclusions. Radiative effects on linear magnetoacoustic slow waves can be a viable mechanism for the spatial damping of short period prominence oscillations, while thermal conduction does not play any role. In particular, short-period oscillations (5−15 min) observed in quiescent limb prominences, which seem to be due to internal fundamental slow modes, have damping lengths in the range 10 4 −5 × 10 4 km, in good agreement with our results.

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A model for quiescent solar prominences

Cited by 49 publications

References 0 publications

Time damping of linear non-adiabatic magnetohydrodynamic waves in an unbounded plasma with solar coronal properties

Time damping of linear non-adiabatic magnetohydrodynamic waves in an unbounded plasma with solar coronal properties

Stability of thermal modes in cool prominence plasmas

Spatial damping of linear non-adiabatic magnetoacoustic waves in a prominence medium

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