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  • 1
    Electronic Resource
    Electronic Resource
    Analytical criteria for nonlinear instability of thermal structures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 4127-4133 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analytical criteria for supercritical and asymptotic stability and for subcritical and superexponential instability are obtained for slab-like, spherical, and cylindrical thermal structures. It is assumed that both, the thermal conductivity κ(T) and the gain/loss function Q(T), can be written as continuous functions of the temperature and they have continuous derivatives. Conditions on κ and Q under which the symmetry of the structure determines the kind of instability (or stability) are obtained. Additionally, it is found that the response of the structure not only depends on the amplitude of the disturbance, but also on whether the disturbance increases or decreases the initial steady temperature. In particular, the threshold value for the amplitude of the disturbances beyond which a linearly stable configuration destabilizes, and explicit conditions for catastrophic heating or cooling are obtained. Applications to structures constituted by atomic and molecular gas are outlined. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871036
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Radiation-condensation instability in a highly ionized dusty plasma (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 3259-3263 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of linear perturbations in a radiatively cooling dusty plasma is considered, with the charge of both dust (Zd) and plasma (Zp) components being allowed to vary with their densities. It is shown that in the long-wavelength limit corresponding to the characteristic cooling length, when the plasma can be treated as quasineutral, the presence of dust particles changes the criteria for radiation instability, regardless of the charging process of the dust particles. In particular, the condensation (isobaric) mode is shown to be stabilized (destabilized) if in the equilibrium, the relation between densities of the dust nd and plasma n under the quasineutrality condition, (d ln nd/d ln n)q〈1 (〉1) is satisfied, while the isentropic mode is stabilized (destabilized) when the opposite inequalities take place; the isochoric mode is unaltered. Numerical estimates show that these effects can be important in hot phases (T∼106 K) of the interstellar plasma, and in tokamak plasma near the walls. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494071
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  • 3
    Electronic Resource
    Electronic Resource
    Nonlinear Evolution of Thermal Structures. Numerical Approach (1997)
    Springer
    Astrophysics and space science 256 (1997), S. 381-386 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A numerical algorithm using a two stage, two level difference scheme has been developed to solve the heat transfer equation with nonlinear heat diffusion and bulk energy losses. The algorithm is an extension of the scheme developed by Meek and Norbury (1982). The first stage calculates an intermediate value which is used in a second stage to estimate a new value. The scheme is consistent, second-order convergent in space and almost second order in time. It has been applied to the nonlinear stability and time evolution of thermal structures constituted by optically thin plasmas with solar abundances. The configuration has been assumed to be heated at a rate ∼ Tm, cooled at a rate ∼ Tn and a thermal conduction coefficient ∼ Tk. In particular, the second order analytical approximation considered in previous papers (Ibáñez and Rosenzweig, 1995; Steele and Ibáñez, 1997) has been worked out for arbitrary amplitude of the initial temperature disturbance. Particular cases of interest in Astrophysics are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001128216905
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  • 4
    Electronic Resource
    Electronic Resource
    Sound and thermal waves propagation in a hydrogen plasma heated by an external radiation field (1990)
    Springer
    Astrophysics and space science 164 (1990), S. 193-211 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal equilibrium of a hydrogen plasma heated and ionized by an external radiation field, diluted by a factorW * and defined by an effective temperatureT *, is studied. In addition, the problem of propagation of acoustic and thermal waves in the above plasma model is also analysed. It is found that an external radiation field has stabilizing effects against wave amplification. From the dispersion relation obtained, the phase velocity $$\tilde v$$ for sound and thermal waves and their respective scale-length of damping (or anti-damping) $$\tilde \omega $$ is calculated as a function of the frequency $$\tilde l$$ for representative values of the plasma temperature $$\tilde T$$ and the external radiation fieldT *.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658824
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  • 5
    Electronic Resource
    Electronic Resource
    Propagating of sound and thermal waves in a reacting fluid (1987)
    Springer
    Astrophysics and space science 137 (1987), S. 1-15 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The propagation of linear sound and thermal waves in a reacting fluid, in which the heating and cooling processes can be represented by a heat-loss functionL(ρ, T, ξ is studied. A complex dispersion relation is found, from which the phase velocity and the scale length for damping (or amplification), of the above two-wave mode are calculated Wave amplification may occur in reacting locally stable fluids. Results are applied to a hydrogen plasma model assumed to be heated at a non-specified constant rate and cooled by recombination, excitation, and ionization by collisions, and free-free transitions. The phase velocity $$\tilde l$$ , the scale-length for damping $$\tilde \upsilon$$ , and the relevant relaxation times are calculated as functions of the dimensionless frequency $$\tilde \omega$$ , for temperatures ranging from those at which the hydrogen plasma is neutral to those at which it becomes completely ionized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00641615
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    Paper (German National Licenses)
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