Upper Atmospheres of Hot Jupiters: Planetary Magnetic Field, Photoionization and Interaction with the Stellar Wind

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AST-0908079ArrasGas giant exoplanets in short-period orbits around their parent star, often referred to as 'hot Jupiters', are exposed to ionizing radiation and a stellar wind flux that are orders of magnitude more intense than for solar system gas giants. Under such conditions, magnetic effects become important. This project will include, for the first time, the intrinsic planetary magnetic field in models of upper atmosphere structure and interaction with the stellar wind, under conditions appropriate to this type of planet. The research study will construct a static model for low magnetic latitudes; a dynamical model for flow along open field lines near the magnetic poles; and will run two-dimensional magnetohydrodynamics simulations of photo-ionization driven outflow from magnetized planets. These models relate to several different observations of hot Jupiters and their host stars. Model composition, density and ionization state profiles will be used to understand the transmission spectra of transiting planets.The intrinsic magnetic field is also crucial for understanding the interaction of the planet with the stellar wind. Existing methods developed for the Jupiter-Io interaction will be applied to understanding the observed time-dependent chromospheric emission from the host stars of some hot Jupiters, as well as the magnetic torques exerted on the planet and how they affect its long term spin and orbital evolution. These important physical effects have been neglected in previous studies of the upper atmospheres of hot Jupiters.This study supports research training of graduate and undergraduate students. The topic of extrasolar planets is of inherent interest to the public, and the research will be used to inform public talks at the McCormick Observatory at the University of Virginia.This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).