Comet 67P/Churyumov–Gerasimenko’s atmosphere

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Table of contents

List of figures
List of tables
1 General introduction
1.1 Flag flapping instability induced by wind
1.2 Granular patterns on an erodible bed
1.3 Sublimation patterns on an ice bed
1.4 Fluid flow over the rippled patterns
1.5 Outline of the thesis
I Travelling waves on highly flexible substrates
2 Paper waves in the wind
2.1 Introduction
2.2 Experimental study
2.2.1 Experimental setup
2.2.2 Experimental data
2.3 Theoretical modelling
2.3.1 Governing equations
2.3.2 Linearized problem
2.3.3 Dispersion relation
2.3.4 Asymptotic analysis and scaling laws
2.4 Comparisons with experiments
2.4.1 Selection of angular frequency and wavenumber
2.4.2 Finite amplitude effects
2.5 Results and Discussions
II Giant ripples on comet 67P/Churyumov-Gerasimenko
3 Introduction
3.1 Comet 67P/Churyumov–Gerasimenko and the Rosetta mission
3.2 Unexpected bedforms on the comet
3.3 Outline of the part
4 Thermo-hydrodynamics of comet 67P/Churyumov–Gerasimenko’s atmosphere
4.1 Gravity
4.2 Thermal process of the comet’s nucleus
4.2.1 Thermal diffusion
4.2.2 Ice sublimation
4.3 Hydrodynamics of the comet’s atmosphere
4.3.1 Outer layer flow
4.3.2 Turbulent boundary layer
4.3.3 Porous sub-surface layer
4.4 Results and discussions
4.4.1 Temperatures, density and pressure
4.4.2 Vapour flux
4.4.3 Wind
4.5 A brief summary
5 Sediment transport
5.1 Grain size
5.2 Transport threshold
5.2.1 Threshold velocity ut
5.2.2 Cohesion
5.2.3 A comparison of ut and u∗
5.2.4 Dependence of ut on d
5.3 Transport mode and saturated transport
5.3.1 Transport mode
5.3.2 Saturated transport flux qsat
5.3.3 Saturation length Lsat
5.4 A brief summary
6 The nature of the bedforms
6.1 Dispersion relation
6.2 Most unstable mode
6.2.1 Wave length selection
6.2.2 Bedform growth and propagation
6.3 Conclusions
III Sublimation dunes on Pluto
7 Introduction
7.1 Pluto and the New Horizons mission
7.2 Rythmic patterns on the surface of Pluto
8 Pluto’s atmosphere
8.1 A general description
8.2 Thermo-hydrodynamics of Pluto’s atmosphere
8.2.1 Thermal processes
8.2.2 Hydrodynamical description
8.3 A brief summary
9 Physical model of sublimation dunes
9.1 Governing equations
9.1.1 Thermal processes
9.1.2 Hydrodynamics
9.1.3 Sublimation interface
9.1.4 Self-illumination on a modulated surface
9.2 Linearised problem
9.2.1 Base state
9.2.2 First order fields
9.2.3 Base state in a dimensionless form
9.2.4 Interfacial equations
9.2.5 Linearised system
9.3 Dispersion relation
9.3.1 Instability due to heat diffusion and convection
9.3.2 Instability due to solar radiation
9.3.3 Application to Pluto
9.4 Conclusions
IV Aeolian sand ripples
10 Aeolian sand ripples instability
10.1 Introduction
10.2 A simplified transport model
10.2.1 Hop length modulation
10.2.2 Flux modulation
10.3 A simplified model for bed evolution
10.4 Discussions
11 Conclusions and perspectives
References