Thermally-driven atmospheric escape evolves from an organized outflow (hydrodynamic escape) to escape on a molecule by molecules basis (Jeans escape) with increasing Jeans parameter, the ratio of the gravitational to thermal energy of molecules in a planet's atmosphere.This transition is described here using the direct simulation Monte Carlo method for a single component spherically symmetric atmosphere. When the heating is predominantly below the lower boundary of the simulation region, R 0 , and well below the exobase, this transition is shown to occur over a surprisingly narrow range of Jeans parameters evaluated at R 0 : λ 0 ~ 2-3. The Jeans parameter λ 0 ~ 2.1 roughly corresponds to the upper limit for isentropic, supersonic outflow and for λ 0 >3 escape occurs on a molecule by molecule basis. For λ 0 > ~6, it is shown that the escape rate does not deviate significantly from the familiar Jeans rate evaluated at the nominal exobase, contrary to what has been suggested. Scaling by the Jeans parameter and the Knudsen number, escape calculations for Pluto and an early Earth's atmosphere are evaluated, and the results presented here can be applied to thermally-induced escape from a number of solar and extrasolar planetary bodies.

The scaling laws describing the thermal conductivity in random networks of straight conducting nanofibers are derived analytically and verified in numerical simulations. The applicability of the scaling laws to more complex structures of interconnected networks of bundles in carbon nanotube (CNT) films and mats is investigated in mesoscopic simulations. The heat transfer in CNT materials is found to be strongly enhanced by self-organization of CNTs into continuous networks of bundles. The thermal conductivity of CNT films varies by orders of magnitude depending on the length of the nanotubes and their structural arrangement in the material.

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9 Phone Number: 1-434-924-3244 10 11 problems. Finally, the recent discovery of CO at high altitudes, the 35 effect of Charon and the conditions at the New Horizon encounter 36 are briefly considered. 37