Angular distributions of electrons elastically scattered from<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Shyn, T. W.; Sharp, William

doi:10.1103/physreva.24.1734

Cited by 96 publications

(52 citation statements)

References 24 publications

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“…The relative importance of the collisional processes is governed by their cross-sections. In this particular realization of the model, we used experimental and calculated data for the cross-sections and distributions of the scattering angles in the elastic, inelastic, and ionization collisions of electrons with H 2 , He, and H taken from the following sources: (a) for electron collisions with H 2 we used the AMDIS database 2 and the work by Shyn & Sharp (1981); and (b) for electron collisions with He and atomic hydrogen, we use the H 2 NIST database 3 and the data from the studies of Jackman et al (1977) and Dalgarno et al (1999).…”

Section: Numerical Modelmentioning

confidence: 99%

Heating efficiency in hydrogen-dominated upper atmospheres

Shematovich

Ionov

Lämmer

2014

A&A

119

106

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Context. The heating efficiency η hν is defined as the ratio of the net local gas-heating rate to the rate of stellar radiative energy absorption. It plays an important role in thermal-escape processes from the upper atmospheres of planets that are exposed to stellar soft X-rays and extreme ultraviolet radiation (XUV). Aims. We model the thermal-escape-related heating efficiency η hν of the stellar XUV radiation in the hydrogen-dominated upper atmosphere of the extrasolar gas giant HD 209458b. The model result is then compared with previous thermal-hydrogen-escape studies, which assumed η hν values between 10-100%. Methods. The photolytic and electron impact processes in the thermosphere were studied by solving the kinetic Boltzmann equation and applying a Direct Simulation Monte Carlo model. We calculated the energy deposition rates of the stellar XUV flux and that of the accompanying primary photoelectrons that are caused by electron impact processes in the H 2 → H transition region in the upper atmosphere. Results. The heating by XUV radiation of hydrogen-dominated upper atmospheres does not reach higher values than 20% above the main thermosphere altitude, if the participation of photoelectron impact processes is included. Conclusions. Hydrogen-escape studies from exoplanets that assume η hν values that are ≥20% probably overestimate the thermal escape or mass-loss rates, while those who assumed values that are <20% produce more realistic atmospheric-escape rates.

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Section: Numerical Modelmentioning

confidence: 99%

Heating efficiency in hydrogen-dominated upper atmospheres

Shematovich

Ionov

Lämmer

2014

A&A

119

106

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“…9. At temperatures typical of Schmidt et al (1994) (empty squares), Shyn & Sharp (1981) (empty circles), Nishimura et al (1985) (filled triangles), Khakoo & Trajmar (1986) (filled squares), Brunger et al (1990Brunger et al ( , 1991 (filled circles). The dashed and dotted curves show the Langevin cross section and the quantum-mechanical theoretical results of Henry & Lane (1969), respectively.…”

Section: E -Hmentioning

confidence: 99%

Three-fluid plasmas in star formation

Pinto

Galli

2008

A&A

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Context. The charged component of the insterstellar medium consists of atomic and molecular ions, electrons, and charged dust grains, coupled to the local Galactic magnetic field. Collisions between neutral particles (mostly atomic or molecular hydrogen) and charged species, and between the charged species themselves, affect the magnetohydrodynamical behaviour of the medium and the dissipation of electric currents. Aims. The friction force due to elastic collisions between particles of different species in the multi-component interstellar plasma is a nonlinear function of the temperature of each species and the Mach number of the relative drift velocity. The aim of this paper is to provide an accurate and, as far as possible, complete set of momentum transfer rate coefficients for magnetohydrodynamical studies of the interstellar medium. Methods. Momentum transfer rates are derived from available experimental data and theoretical calculations of cross sections within the classic approach developed by Boltzmann and Langevin for a wide range of values of the temperature and the drift velocity. Results. Accurate numerical values for momentum transfer rates are obtained and fitted to simple analytical formulae expressing the dependence of the results on the gas temperature and the relative drift velocity. The often used polarization approximation is in satisfactory agreement with our results only for collisions between H 2 and molecular ions (HCO + , H + 3 ). For other kinds of collisions, the polarization approximation fails by large factors, and must be replaced by more accurate expressions.

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“…͑12͒ is in good agreement with the available experimental data. 5,9 The experimental momentum transfer cross section m (E) is also available 10,11 and is plot- ted in Fig. 7.…”

Section: ͑8b͒mentioning

confidence: 99%