In the space physics and surface physics theory program at the University of Virginia, we study the physics and chemistry of energetic ion, electron and UV-photon interactions with surfaces and gases. The processes of interest are desorption and sputtering, the radiolysis and photolysis of surfaces, and atmospheric evolution. The motivation for these studies is to interpret observations in astronomy. Of particular interest is the coupling of the surfaces and atmospheres of the moons of Jupiter and Saturn with the trapped plasma in the planetary magnetospheres. We also study photon and cosmic ray ion interactions with Kuiper Belt objects and with grains in the interstellar medium and in young stellar objects.
To interpret observations and to understand the physical processes we carry out molecular dynamic and Monte Carlo descriptions of radiation interaction with materials, determining sputtering yields and chemical changes, we calculate new collision cross-sections, and Monte Carlo models of loss of atmosphere. In this effort, we collaborate with a number of laboratory groups. We use this data to model telescope and spacecraft observations and we are a partner on the Cassini mission to Saturn.
- Atmospheric, Ionospheric, and Energetic Radiation Environments of Saturn’s Rings Cooper, J.F, Edward C. Sittler, Robert E. Johnson, Peter Kollman, Elias Roussos. Chap. In Saturn's Rings. 2016
- Surface Interaction Contributions to the Lunar Exosphere Dukes, C and R.E. Johnson. Chapt in Encyclopedia of Lunar Science, ed. B. Cudnik. Submitted (2016)
- Evolution of an Early Titan Atmosphere Johnson, R.E., A.N. Volkov, O.J. Tucker. Icarus 271, 202-206 (2016)