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Title: ANALYTICAL MODELS OF EXOPLANETARY ATMOSPHERES. I. ATMOSPHERIC DYNAMICS VIA THE SHALLOW WATER SYSTEM

Within the context of exoplanetary atmospheres, we present a comprehensive linear analysis of forced, damped, magnetized shallow water systems, exploring the effects of dimensionality, geometry (Cartesian, pseudo-spherical, and spherical), rotation, magnetic tension, and hydrodynamic and magnetic sources of friction. Across a broad range of conditions, we find that the key governing equation for atmospheres and quantum harmonic oscillators are identical, even when forcing (stellar irradiation), sources of friction (molecular viscosity, Rayleigh drag, and magnetic drag), and magnetic tension are included. The global atmospheric structure is largely controlled by a single key parameter that involves the Rossby and Prandtl numbers. This near-universality breaks down when either molecular viscosity or magnetic drag acts non-uniformly across latitude or a poloidal magnetic field is present, suggesting that these effects will introduce qualitative changes to the familiar chevron-shaped feature witnessed in simulations of atmospheric circulation. We also find that hydrodynamic and magnetic sources of friction have dissimilar phase signatures and affect the flow in fundamentally different ways, implying that using Rayleigh drag to mimic magnetic drag is inaccurate. We exhaustively lay down the theoretical formalism (dispersion relations, governing equations, and time-dependent wave solutions) for a broad suite of models. In all situations, we derive themore » steady state of an atmosphere, which is relevant to interpreting infrared phase and eclipse maps of exoplanetary atmospheres. We elucidate a pinching effect that confines the atmospheric structure to be near the equator. Our suite of analytical models may be used to develop decisively physical intuition and as a reference point for three-dimensional magnetohydrodynamic simulations of atmospheric circulation.« less
Authors:
 [1] ;  [2]
  1. Center for Space and Habitability, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland)
  2. Colorado Mesa University, 1260 Kennedy Avenue, Grand Junction, CO 81501 (United States)
Publication Date:
OSTI Identifier:
22340185
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 213; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATMOSPHERIC CIRCULATION; DISPERSION RELATIONS; DRAG; ECLIPSE; EQUATOR; HARMONIC OSCILLATORS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PINCH EFFECT; PLANETARY ATMOSPHERES; PLANETS; PRANDTL NUMBER; QUANTUM MECHANICS; ROTATION; SIMULATION; SPHERICAL CONFIGURATION; STEADY-STATE CONDITIONS; THREE-DIMENSIONAL CALCULATIONS; WATER