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

AST-0908079ArrasGas巨型系外行星围绕其母恒星运行的短周期轨道上，通常被称为“热木星”，暴露在电离辐射和恒星风通量中，其强度比太阳系气体巨行星强几个数量级。在这种情况下，磁效应变得很重要。该项目将首次在适合这类行星的条件下，在高层大气结构和与恒星风相互作用的模型中包括行星的固有磁场。这项研究将建立一个低磁纬度的静态模型；一个沿磁极附近开放场线流动的动态模型；并将对磁化行星的光致电离驱动的外流进行二维磁流体动力学模拟。这些模型涉及对热木星及其宿主恒星的几种不同的观测。模型的组成、密度和电离态分布将被用来理解凌日行星的透射谱。本征磁场对于理解行星与恒星风的相互作用也是至关重要的。为木星-木卫一相互作用开发的现有方法将被用于理解从一些热木星的宿主恒星观测到的随时间变化的色球辐射，以及施加在行星上的磁矩，以及它们如何影响其长期自转和轨道演化。这些重要的物理效应在以前对热木星高层大气的研究中被忽略了。这项研究支持研究生和本科生的研究性训练。太阳系外行星的话题是公众固有的兴趣，这项研究将被用于在弗吉尼亚大学麦考密克天文台的公开演讲。该奖项由2009年美国复苏和再投资法案(公法111-5)资助。

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).