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Plasma Interactions with Atmospheres and Surfaces

Wednesday, April 14, 2010 - 4:00pm

CCU Lecture Series, National Radio Astronomy Observatory, Charlottesville


Robert E. Johnson

Robert E. Johnson

John Lloyd Newcomb Professor of Engineering Physics and Materials Science

University of Virginia, Charlottesville, VA 22904


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Understanding the data returned from spacecraft and telescopic exploration of the outer solar system often requires an understanding of the effect of space plasmas on the surfaces and atmospheres of bodies. For example, the icy satellites in the outer solar system are bombarded by relatively intense fluxes of ions and electrons, as well as the background solar UV flux, causing changes in their optical reflectance and ejection of molecules from their surfaces. The low cohesive energy of ice and the chemistry induced by the incident radiation can result in relatively large rates of molecular desorption. The ejected molecules produce an ambient gas about an icy body that is, in turn, often the principal source of the local plasma, resulting in an interesting feedback process. Similarly, plasma ions can flow onto the atmosphere of a body that does not have a magnetic field (e.g., Mars, Titan and Pluto) driving escape and altering the composition and, thereby, affecting the atmospheric evolution. In this talk I will describe our work on the physics and chemistry required to model these problems with emphasis on results from the Cassini spacecraft and the modeling in advance of a number of proposed missions.