Evolution and saturation of Autowaves in photodissociation regions

Krasnobaev, K. V.; Tagirova, R. R.; Arafailov, S. I.; Kotova, G. Yu.

doi:10.1134/s1063773716070057

Cited by 19 publications

(8 citation statements)

References 25 publications

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“…The astrophysical media with adiabatic instability have been recently discussed in [22][23][24][25][26][27][28]. Papers [24,26,[28][29][30][31][32][33] were devoted to the features of the nonlinear magnetosound waves distortions and nonlinear interaction of waves in a magnetic fluid flow. The acoustical activity and nonlinear phenomena in acoustically active media have counterparts in many flows with other kind of anomalous thermodynamic relaxation corresponding dispersion: in flows of gases with excited vibrational degrees of molecules and chemically reacting gases.…”

Section: Discussionmentioning

confidence: 99%

Magnetoacoustic Heating in Nonisentropic Plasma Caused by Different Kinds of Heating-Cooling Function

Perelomova

2018

Advances in Mathematical Physics

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The nonlinear phenomena which associate with magnetoacoustic waves in a plasma are analytically studied. A plasma is an open system with external inflow of energy and radiation losses. A plasma’s flow may be isentropically stable or unstable. The nonlinear phenomena occur differently in dependence on stability or instability of a plasma’s flow. The nonlinear instantaneous equation which describes dynamics of nonwave entropy mode in the field of intense magnetoacoustic perturbations is the result of special projecting of the conservation equations in the differential form. It is analyzed in some physically meaningful cases; those are periodic magnetoacoustic perturbations and particular cases of heating-cooling function. A plasma is situated in the straight magnetic field with constant equilibrium magnetic strength which form constant angle with the direction of wave propagation. A plasma is initially uniform and equilibrium. The conclusions concern nonlinear effects of fast and slow magnetoacoustic perturbations and may be useful in direct and inverse problems.

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Section: Discussionmentioning

confidence: 99%

Magnetoacoustic Heating in Nonisentropic Plasma Caused by Different Kinds of Heating-Cooling Function

Perelomova

2018

Advances in Mathematical Physics

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“…Studies of the isentropic mode (Krasnobaev & Tarev 1987;Krasnobaev, Sysoev & Tarev 1994;Molevich et al 2011) show that the growth of initially small perturbations at the non-linear evolution stage is accompanied by the formation of a sequence of self-sustained shock waves (autowaves). Krasnobaev et al (2016) found numerically that the waves reach saturation and hence have a maximum amplitude that is determined by the heat-loss function Q and depends weakly on the parameters of the initial perturbations (wavelength λ and amplitude a). We assume that λ = 2l 0 .…”

Section: Evolution Of Unstable Perturbationsmentioning

confidence: 96%

Isentropic thermal instability in atomic surface layers of photodissociation regions

Krasnobaev

Tagirova

2017

Monthly Notices of the Royal Astronomical Society

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We consider the evolution of an isentropic thermal instability in the atomic zone of a photodissociation region (PDR). In this zone, gas heating and cooling are associated mainly with photoelectric emission from dust grains and fine-structure lines ([C ii] 158, [O i] 63, and [O i] 146 µm), respectively. The instability criterion has a multiparametric dependence on the conditions of the interstellar medium. We found that instability occurs when the intensity of the incident far-ultraviolet field G 0 and gas density n are high. For example, we have 3 × 10 3 < G 0 < 10 6 and 4.5 × 10 4 < n < 10 6 cm −3 at temperatures 360 < T < 10 4 K for typical carbon and oxygen abundances ξ C = 1.4 × 10 −4 and ξ O = 3.2 × 10 −4 . The instability criterion depends on the relation between ξ C and ξ O abundances and line opacities. We also give examples of observed PDRs where instability could occur. For these PDRs, the characteristic perturbation growth time is t inst ∼ 10 3 -10 4 yr and the distance characterizing the formation of secondary waves is L ∼ 10 −3 -5 × 10 −2 pc. For objects that are older than t inst and have sizes of the atomic zone larger than L, we expect that instability influences the PDR structure significantly. The presence of multiple shock waves, turbulent velocities of several kilometers per second and inhomogeneities with higher density and temperature than the surrounding medium can characterize isentropic thermal instability in PDRs.

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“…Следует отметить, что это условие совпадает с условием существования отрицательного коэффициента второй вязкости [2,3]. Как показано в работах [3][4][5][6], условие изоэнтропической тепловой неустойчивости выполняется в ряде областей межзвездной среды. Кроме того, изоэнтропически неустойчивые области существуют в солнечной короне [3,[7][8][9] и могут быть одной из причин фиксируемых аппаратами (SOHO, Hinode, STEREO, TRACE и др.)…”

Section: поступило в редакцию 7 августа 2018 гunclassified

“…Разумеется, для наблюдения такой картины необходимо, чтобы размер тепловыделяющей среды превышал характерный масштаб усиления. Такие условия могут выполняться в астрофизических системах [3][4][5][6][7][8][9][10]. Также показано, что фронт возмущения давления, обладающий поперечной модуляцией, распадается на систему плоских фронтов, поперечное сечение которых демонстрирует качественное и количественное согласие с видом импульсных автоволн (решениями ОНАУ).…”

Section: поступило в редакцию 7 августа 2018 гunclassified

Двумерные Автоволновые Газодинамические Структуры В Изоэнтропически Неустойчивом Тепловыделяющем Газе

Riashchikov¹,

Molevich²,

Завершинский³

2018

Письма В Журнал Технической Физики

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The evolution of gas-dynamic perturbations in a heat-releasing medium was investigated in two-dimensional geometry under conditions of isentropic instability. Decomposition of the initial perturbation of “step” type, possessing transversal modulation (ripples) of front, into a sequence of flat autowave fronts predicted by a generalized nonlinear acoustic equation is shown. Evolution of localized perturbation results in decomposition into sequence of concentric autowaves. The front of two-dimensional structures is resistant to transversal modulation. A quasi-regular cellular structure is formed behind the fronts.

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Evolution and saturation of Autowaves in photodissociation regions

Cited by 19 publications

References 25 publications

Magnetoacoustic Heating in Nonisentropic Plasma Caused by Different Kinds of Heating-Cooling Function

Magnetoacoustic Heating in Nonisentropic Plasma Caused by Different Kinds of Heating-Cooling Function

Isentropic thermal instability in atomic surface layers of photodissociation regions

Двумерные Автоволновые Газодинамические Структуры В Изоэнтропически Неустойчивом Тепловыделяющем Газе

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