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

气态巨行星在围绕其母恒星的短周期轨道上运行，通常被称为“热木星”，它们暴露在电离辐射和恒星风通量中，其强度比太阳系气态巨行星高几个数量级。在这种条件下，磁效应变得重要起来。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固有的行星磁场。本研究将建立低磁纬地区的静态模型；磁极附近开放磁场线流动的动力学模型并将运行二维磁流体动力学模拟光电离驱动的外流从磁化行星。这些模型与对热木星及其主星的几种不同观测有关。模型的组成、密度和电离态分布将用于了解凌日行星的透射光谱。固有磁场对于理解行星与恒星风的相互作用也是至关重要的。研究木星-木卫一相互作用的现有方法将被应用于了解一些热木星的宿主恒星所观测到的随时间变化的色球发射，以及施加在行星上的磁力矩以及它们如何影响其长期自旋和轨道演化。这些重要的物理效应在以前对热木星上层大气的研究中被忽略了。本研究支持研究生和本科生的研究训练。系外行星的话题是公众固有的兴趣，这项研究将用于弗吉尼亚大学麦考密克天文台的公开演讲。该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。

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).