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6.24.14 Tucker

INSIGHT INTO PLUTO’S ATMOSPHERIC STRUCTURE FROM MOLECULAR KINETIC MODELS

O.J. Tucker, University of Michigan
June 24, 2014, 1:00 pm, NIA, Rm 141

Abstract:
In July of 2015 the New Horizons (NH) spacecraft will encounter the Pluto-¬‐Charon system providing scientists with an opportunity to evaluate ideas about Pluto’s atmospheric structure. Recently, the direct simulation Monte Carlo (DSMC) method was used to demonstrate that Pluto’s atmosphere is likely warmer and more extended than previously estimated using hydrodynamic models (Tucker et al. 2012, Erwin et al. 2013). The exobase radius is estimated to be less than 2 Pluto radii from Charon’s Roche Lobe for solar conditions expected during NH, and the gas molecules from Pluto’s exobase impinge upon Charon occurs at rates of ~1025 N2/s (Tucker et al. 2014). This transfer rate is sufficient to produce a Charon atmosphere with near surface line of sight column densities, ~1018 – 1019 N2/m2, that could be detectable during the solar occultation that will occur during the NH mission. In addition, Pluto’s extended atmosphere may serve as a barrier shielding Charon from the unperturbed solar wind. Remote sensing data of Charon’s atmosphere can provide a measure for the gas transfer rates, and in-¬‐ situ plasma measurements of the mass loaded solar wind at the Pluto-¬‐Charon system can be used to infer the molecular escape rate from Pluto (e.g., Delamere 2009) to test simulations of gas transfer in binary systems. The talk will cover the recent findings.

Delamere, P A. “Hybrid code simulations of the solar wind interaction with Pluto.” J. Geophys. Res. 114, no. A03220 (2009): 1-¬‐17.

Erwin, J T, O J Tucker, and R E Johnson. “Hybrid fluid/kinetic modeling of Pluto’s escaping atmosphere.” Icarus 226 (2013): 375-¬‐385.

Tucker, O J, J T Erwin, J I Deighan, A N Volkov, and R E Johnson. “Thermally driven escape from Pluto’s atmosphere: A combined fluid/kinetic model.” Icarus 217 (2012): 408-¬‐415.

Tucker, O J, R E Johnson, and L A Young. “Gas Transfer in the Pluto-¬‐Charon system: A Charon Atmosphere.” Icarus In Press (2014).

Bio:
O.J. Tucker is a postdoctoral research fellow in the Atmospheric Oceanic and Space Sciences Department at the University of Michigan. At U of M he develops computational models to study the dynamics occurring in the upper atmospheres of planetary bodies, and uses the simulations to analyze and interpret remote sensing and spacecraft data. His current projects include modeling the geysers on the moon Enceladus, molecular escape from Titan’s upper atmosphere, gas transfer from Pluto’s atmosphere to its moon Charon, and the Moon’s surface generated atmosphere. O.J. Tucker obtained his M.S. and Ph.D degrees in Engineering Physics at the University of Virginia and his B.S. degree in Math-¬‐Physics at Hampden-¬‐Sydney College.

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