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

Journal Article · Fri Aug 01 00:00:00 EDT 2014 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/213/2/27· OSTI ID:22340185

Heng, Kevin ^[1]; Workman, Jared ^[2]

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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)

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 the 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.

• OSTI ID: 22340185
• Journal Information: Astrophysical Journal, Supplement Series, Vol. 213, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0067-0049
• Country of Publication: United States
• Language: English

Related Subjects

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