Radiative Thermal Conductivity of the Lower Mantle Emma Rainey Abby Kavner Laurent Pilon
Core Mantle Q CMB Lay et al., 2008 Lower Mantle Thermal Conductivity Better constraints on k mantle needed
Heat Conduction Mechanisms Two mechanisms likely control heat flow in lower mantle thermal boundary layer Relative importance not well-known Lattice VibrationsRadiation Courtesy of B. Greenhagen
Heat Conduction Mechanisms Two mechanisms likely control heat flow in lower mantle thermal boundary layer Relative importance not well-known Lattice VibrationsRadiation Courtesy of B. Greenhagen
Diffusive Radiative Heat Transfer k rad depends on two optical properties: – Index of refraction (n ) – Absorption coefficient ( ) Grain size (10 -3 m) Photon absorption length (10 -4 m) T across grain < K Thermal boundary layer (10 5 m) Phonon scattering length (10 -9 m) Mantle Scales
Mantle Index of Refraction Model Dominant high P/T effect on n expected to be from density n scales linearly with density for minerals n 1.8 – 2.2 in lower mantle n = Anderson and Schreiber, 1965 density Refractive index
High-Pressure Absorption Coefficient of (Mg,Fe)SiO 3 Perovskite Goncharov et al., 2008 Keppler et al., 2008 pressure
k rad (T) of Major Lower Mantle Phases Perovskite P P Keppler et al. Goncharov et al.
k rad (T) of Major Lower Mantle Phases Perovskite P P P P Keppler et al. Goncharov et al. 6% Fe 15% Fe 25% Fe Ferropericlase (Mg,Fe)O absorption coefficients from Goncharov et al., 2006 and 2009 P
k rad vs. Mantle Depth Perovskite (Keppler et al.) Perovskite (Goncharov et al.) Ferropericlase
Composite Mantle k rad Data from Goncharov et al. Data from Keppler et al. Composite mantle: 80% Pv + 20% Fp q Series Parallel q
Summary k rad at CMB 1-4 W/m·K Sensitivity of k rad to mantle properties: Iron content has large effect compared to temperature Individual phases and phase configuration have significant effect Calculated k rad is upper bound Neglected scattering and minor impurities
BACKUPS
Index of Refraction and Temperature Profiles