@article {409,
title = {Velocity distributions of energetic atoms in planetary exospheres from dissociative recombination},
journal = {Journal of Geophysical Research-Planets},
volume = {107},
number = {E7},
year = {2002},
note = {ISI Document Delivery No.: 610UBTimes Cited: 3Cited Reference Count: 47},
month = {Jul},
pages = {9},
type = {Article},
abstract = {[1] A kinetic theory description of translational energetic atoms in the upper planetary atmosphere is presented. A new analytical result for the velocity distribution of the products of reactive collisions is described. Our calculation takes into account different temperatures of the reactants and arbitrary dependence of the cross section on the relative velocity of the colliding particles. The final result is applied to the production of hot oxygen and carbon by dissociative recombination of O-2(+) and CO+, respectively. The nascent distribution of hot atoms generated in this way is compared with the earlier Monte Carlo calculations. We use the Boltzmann equation to study the thermalization of the hot oxygen via collisions with the thermal oxygen population. The results of this calculation demonstrate quasi-steady state velocity distribution of high-energy oxygen atoms near the exobase of Venus for daytime conditions.},
keywords = {Boltzmann equation, CROSS-SECTIONS, dissociative recombination, ESCAPE, gas kinetic, hot atoms, HOT OXYGEN-ATOMS, HYDROGEN, ION STORAGE-RING, MARS, MONTE-CARLO, NITROGEN-ATOMS, theory, UPPER-ATMOSPHERE, VENUS},
isbn = {0148-0227},
url = {://000178978400004},
author = {Kabin, K. and Shizgal, B. D.}
}
@inbook {5198,
title = {Hot oxygen in the exosphere of Venus},
booktitle = {Rarefied Gas Dynamics},
series = {Aip Conference Proceedings},
volume = {585},
year = {2001},
note = {ISI Document Delivery No.: BT38RTimes Cited: 1Cited Reference Count: 35Proceedings Paper22nd International Symposium on Rarefied Gas DynamicsJUL 09-14, 2000SYDNEY, AUSTRALIASandia Natl Labs, AFOSR/AOARD, ONR IFO Asia, Far E, DLR, USA Res Off, GAB Consulting Pty Ltd, Telstra2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA},
pages = {119-126},
publisher = {Amer Inst Physics},
organization = {Amer Inst Physics},
address = {Melville},
abstract = {It has now been firmly established from both theoretical calculations and observations, that the exospheres of the terrestrial planets have extended coronas of translational energetic oxygen atoms. The current model generally accepted as the source of these hot atoms is the dissociative recombination of OZ, that is, O-2(+) + e(-) {\textendash}> O* + O* where the product O* atoms are translationally energetic. The determination of the extent of this population of superthermal atoms is an important endeavor. The present paper considers a simple model based on the Boltzmann equation for the energy and altitude dependence of the oxygen atom distribution function. The density and temperature distributions are determined with this distribution.},
keywords = {ESCAPE, FRACTIONATION, GEOCORONA, HYDROGEN, KINETICS, MARS, MODEL, NITROGEN-ATOMS, O(P-3) ATOMS, UPPER-ATMOSPHERE},
isbn = {0094-243X0-7354-0025-3},
url = {://000172834300017},
author = {Shizgal, B. D.},
editor = {Bartel, T. J. and Gallis, M. A.}
}
@article {3120,
title = {DISCRETE VELOCITY MODEL FOR AN ESCAPING SINGLE-COMPONENT ATMOSPHERE},
journal = {Planetary and Space Science},
volume = {42},
number = {5},
year = {1994},
note = {ISI Document Delivery No.: PF109Times Cited: 3Cited Reference Count: 42},
month = {May},
pages = {409-419},
type = {Article},
abstract = {The structure of an escaping single-component planetary atmosphere is computed by direct numerical integration the nonlinear Boltzmann equation. The transition from collision-dominated behavior deep in the atmosphere to nearly collisionless behavior at great altitudes is therefore treated self-consistently for the first time. We consider a hypothetical planet having the same mass and radius as the Earth, surrounded by an atmosphere of atoms having the same mass and total hard-sphere collision cross-section as atomic hydrogen. The atmosphere is initially hydrostatic and isothermal, at a temperature of 1000 K. As the computation progresses, the atmosphere gradually escapes. Eventually, a quasi-steady state is reached in which the density decreases significantly more rapidly than the initial barometric distribution, and the temperature decreases nearly 200 K between the planetary surface and an altitude of 10,000 km. The bulk upward flow speed increases with altitude above the exobase. However, because the most energetic particles escape and are not replenished, the atmosphere gradually cools, and the deep, collision-dominated portion of the atmosphere settles towards the planet{\textquoteright}s surface. The high-velocity tail of the velocity distribution function is quite anisotropic over a large range of altitudes, and remains largely depleted of incoming unbound particles even well below the exobase. At the highest altitudes in our simulation, the population of escaping unbound particles is considerably enhanced by the streaming of such particles from the warmer and denser regions below. The computed escape flux is at least 30\% greater than the Jeans flux as a result of this effect. It is suggested that computations similar to this one may prove useful for studying atmospheric escape from the primeval terrestrial planets, comets and Pluto.},
keywords = {BOLTZMANN-EQUATION, ESCAPE, GASES, HYDRODYNAMIC ESCAPE, PLANETARY ATMOSPHERE, thermal},
isbn = {0032-0633},
url = {://A1994PF10900006},
author = {Merryfield, W. J. and Shizgal, B. D.}
}
@article {2995,
title = {RELAXATION DYNAMICS OF HOT PROTONS IN A THERMAL BATH OF ATOMIC-HYDROGEN},
journal = {Physical Review E},
volume = {49},
number = {1},
year = {1994},
note = {ISI Document Delivery No.: MV514Times Cited: 10Cited Reference Count: 58},
month = {Jan},
pages = {347-358},
type = {Article},
abstract = {We present a rigorous kinetic theory formulation of the relaxation of hot protons (H+) in a bath of thermal atomic hydrogen (H). We apply the (well-known) quantum-mechanical scattering theory to (H+,H) collisions and calculate the differential elastic cross section as a function of collision energy and scattering angle. This calculation includes the effects Of both direct and charge-exchange scattering. We then solve the time-dependent Boltzmann equation numerically for the H+ distribution function with an initial delta-function distribution. We also consider two approximate models for the collision dynamics, each based on the assumption that charge exchange dominates the relaxation and that no momentum is transferred in a collision (the linear-trajectory approximation). The first model uses the Rapp-Francis [J. Chem. Phys. 37, 2631 (1962)] energy-dependent cross section in the exact kernel which defines the Boltzmann collision operator. The second model uses a hard-sphere cross section in an approximate collision kernel. We compare the relaxation behavior calculated with the approximate formulations with the exact solution. We also calculate the mobility of H+ in H and compare the exact and-approximate; formulations. This study has applications to processes in astrophysics and aeronomy such as the non-thermal escape of H from planetary atmospheres.},
keywords = {CHARGE-EXCHANGE, COLLISION KERNELS, EIGENVALUES, ENERGIES, equation, ESCAPE, EXOSPHERE, TRANSPORT, VENUS},
isbn = {1063-651X},
url = {://A1994MV51400048},
author = {Clarke, A. S. and Shizgal, B.}
}