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  • 1995-1999  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Energy deposition due to the dissipation of dust-acoustic waves (1996)
    Springer
    Astrophysics and space science 240 (1996), S. 235-239 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the total energy dissipation rate of a dust-acoustic wave on a uniform background medium, in which the dust is not a dominant charge carrier, as a function of the dust-acoustic wavelength and dust parameters and give results for the deposition rates in each of the dust, ion and electron fluids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00639588
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Multifluid models of shocks in magnetized interstellar molecular clouds (1995)
    Springer
    Astrophysics and space science 233 (1995), S. 97-109 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In a weakly ionized magnetized medium the dissipation in a shock moving at a speed sufficiently below the speed of high frequency hydromagnetic waves occurs on a lengthscale that is very large compared to any of the collision lengths. Chemistry affects the structures of these continuous or ‘C-type’ shocks which are sometimes unstable. In dark cloud shocks grain-neutral friction is an important dissipation process, and the adoption of a fluid description of grain dynamics elucidates various effects which include the onset of anE ×B drift-driven runaway in some perpendicular shocks. The imperfect nature of the conductivity in the clouds may cause significant rotation of the magnetic field about the shock propagation direction in a dense cloud shock. Models of shocks in which continuous dissipation is important have been developed in studies of the origins of CH+ in diffuse clouds, H2 emission features with widths of around 100 km s−1 in Orion and OH masers around young stars, but CH+ and such broad H2 features may arise in boundary layers between molecular regions and fast flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627338
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Comments on some possible models of TMC-1 (1996)
    Springer
    Astrophysics and space science 238 (1996), S. 303-308 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Chemical differences between cores in the dark ridge TMC-1 have been attributed to the cores being in different stages of chemical evolution with those having high NH3 to cyanopolyyne abundance ratios being the most evolved. We suggest several alternative models including one in which the highest NH3 to cyanopolyyne abundance ratio obtains in the youngest TMC-1 core; in this and in one of the other models the evolution of the chemistry as depletion increases is supposed to lead to a lower NH3 to cyanopolyyne ratio. The possibility that the cyanopolyynes exist primarily in an interface between dark core material and the wind of a low mass star is considered; this wind interface model may account for the sharp cyanopolyyne emission gradient on the side of the ridge away from the star. Implosion of the cores by the ram pressure of the wind may have caused them to collapse more rapidly than gravity could and more rapidly than chemistry evolves so that the chemistry reflects a core's state at a lower density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00641694
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dusty plasmas in interstellar clouds and star forming regions (1996)
    Springer
    Astrophysics and space science 246 (1996), S. 243-289 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We provide an introduction to self-consistent theoretical models of interstellar dynamics in which dust is treated on a footing equal to that adopted for the description of the gaseous components of the media. Simple background material on the natures of interstellar clouds, dust, and star forming regions is given in the hopes that this review will be accessible to scientists and students interested in a broad range of nonastronomical dusty plasmas as well as to astrophysicists. The main emphasis is on the effects of dust on the damping of waves in clouds, on ambipolar diffusion in star formation, and on the structures of shocks driven into the interstellar clouds by the winds from recently formed stars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645644
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular diagnostics of diffusive boundary layers (1995)
    Springer
    Astrophysics and space science 233 (1995), S. 161-164 
    Details
    ISSN: 1572-946X
    Keywords: Stars ; Chemistry ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have assessed the role of diffusion in determining chemical abundances in molecular interface regions. Chemical models have been developed which include the appropriate diffusion terms and that are appropriate to a narrow diffusion region (∼0.01pc) that may exist at the interface between a dark core and a hot, shocked T-Tauri wind. We have assumed pressure balance throughout and have calculated the chemical abundances as functions of time and position through the interface. The results show that significant enhancements of detectable molecules/transitions are expected (e.g. CO J=6→5, OH and CH). Using a realistic value of the diffusion coefficient a diffusive region of dimension 0.01pc may be established within about 104 years. In general it seems likely that diffusion processes are highly significant on these and smaller lengthscales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627344
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Wide intermediate scale structures in mass-loaded flows (1996)
    Springer
    Astrophysics and space science 235 (1996), S. 165-168 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We showed in earlier work that a clump embedded in tenuous plasma, which is flowing subsonically relative to the clump, will develop a long thin tail whether the gas in the tail behaves adiabatically or isothermally. This paper presents a criterion for determining if viscous dissipation in a tail with result in heating that will cause such a tail to be wide. We argue that the observed properties of the tails in NGC 7293 imply that a very strong effective viscous couple exists across each of them. Assuming a strong couple, we calculate the viscous energy dissipation rate per unit volume and derive an upper bound on the number density in a tail in which viscous heating raises the temperature significantly and thus causes broadening. The densities in observed broad tails in Abell 30 exceed this upper bound, and we suggest that the broadening of those tails is due to a phase transition in the tail gas, caused by photo-absorption heating. We comment on the relationship of intermediate-scale structures in clumpy media to the issue of whether or not a global tenous flow can be considered to be mass-loaded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00643600
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular diagnostics of the interstellar medium and star forming regions (1996)
    Springer
    Astrophysics and space science 237 (1996), S. 267-298 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Selected examples of the use of observationally inferred molecular level populations and chemical compositions in the diagnosis of interstellar sources and processes important in them (and in other diffuse astrophysical sources) are given. The sources considered include the interclump medium of a giant molecular cloud, dark cores which are the progenitors of star formation, material responding to recent star formation and which may form further stars, and stellar ejecta (including those of supernovae) about to merge with the interstellar medium. The measurement of the microwave background, mixing of material between different nuclear burning zones in evolved stars and turbulent boundary layers (which are present in and influence the structures and evolution of all diffuse astrophysical sources) are treated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02424435
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Flows in clumpy planetary nebulae (1996)
    Springer
    Astrophysics and space science 245 (1996), S. 263-273 
    Details
    ISSN: 1572-946X
    Keywords: Planetary nebulae ; Hydrodynamics ; Multi-phase flows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamics of clumps observed in planetary nebulae are considered. The possibility that SiO maser spots in evolved stars and the planetary nebula clumps are formed by the Parker instability behind shocks in pulsating stars' atmospheres is raised. Molecular observations of the clumps are suggested. The effects of the ablation of clumps on the global flow structure of a more tenuous plasma in which they are embedded are reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00642231
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    Paper (German National Licenses)
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