2:57 PM, Dec. 8, 2012 CIDER Post-AGU 2012 “Snowfall” in F Layer Jie (Jackie) Li University of...
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Transcript of 2:57 PM, Dec. 8, 2012 CIDER Post-AGU 2012 “Snowfall” in F Layer Jie (Jackie) Li University of...
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2:57 PM, Dec. 8, 2012
CIDER Post-AGU 2012
“Snowfall” in F Layer
Jie (Jackie) LiUniversity of Michigan
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Collaborators
Jeffrey Pigott – Mineral Physics (Ohio State)Jie (Jackie) Li – Mineral Physics (U of Michigan)Bin Chen – Mineral Physics (U of Michigan)Matt Armentrout – Mineral Physics (UCLA)Antonio Buono – Mineral Physics (MIT)
John Hernlund – Geodynamics (UC-Berkeley)Jodi Gaeman – Geodynamics (U of Maryland)
Lauren Waszek – Seismology (Cambridge)
Louis Kellogg, Barbara Romanowicz, Jeroen Tromp, Vernon Cormier
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Seismic features of the F-layer
Outer Core
Inner Core
F-layer
PREMAK135PREM2
Zou et al. 08Krasnoshchekov et al. 05Cao et al. 07Sun and Song 08Gubbins et al. 08,
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“Snowing” cores in Solar System
Williams 09 Hauck et al. 06 JGRChen et al. 08 GRL
Stewart et al. 07 Science
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Occurrence of “snowfall” in Earth’s core?Case 1
Case 2
Case 1Melting gradient
decreases
Case 2Adiabatic gradient
increases
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Integrative approachMP
- Adiabat, melting curve for snow criterion- Density for dynamic modeling- Velocity for seismic comparison
Seismo- Compare PKIKP-PKiKP differential travel time with PREM- Compare PKIKP-PKiKP differential travel time b/w east-west hemispheres
Dynamics- Evolution of thermal, compositional, and structural profiles with time- Origin of stratified layer- Stability of F-layer
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Adiabatic temperature gradient
Core adiabat(dT/dP)S = gth•T/Kliq
gth: 1.65Kliq: 1343T: geotherm
Perturbation to geotherm
Dziewonski and Anderson 81
Anderson O. 98
Greff-Lefftz and Legros 99,
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Melting curveLindemann’s Law for fixed compositiondTm/dP = 2(gSL – 1/3)•Tm/Ksol
2(gSL – 1/3) = K’ -1, K’ = 1.7 to 3.6Ksol: 1500Tm: melting temperature
Binary solution
Dziewonski and Anderson 81
Seagle et al. 09
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Grüneisen parameters
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Case 1a: Wide “Snowing zone”
Parameter space for “snowing”
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Case 1b: Narrow “snowing” zone
Chen et al. 08
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Case 2:
Greff-Lefftz and Legros 99,
Temperature near ICBincreases due to resonant period and viscomagnetic friction power
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Looking back 2010 July-Aug: CIDER Boundary Layer, KITP 2010 Nov: MP Mini-Meeting Umich 2010 Dec: AGU presentation, meeting 2011 Nov: MP Mini-Meeting Umich 2011 Dec: AGU presentation, Post-AGU CIDER
Workshop 2012 Sep: MP Mini-Meeting Umich
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Tips and TrapsAccomplishments- Cross-discipline exchange- MP collaboration that otherwise would not have occurred- AGU presentations (Li, Hernlund)- SEDI grant (Hernlund and Cormier)- Thesis project (Piggot)
Obstacles- Define leadership role- Follow up- Generate a concrete product
For discussion- Group, ungroup, regroup
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Looking forward2012 has been an eventful year for the groupnew-year resolution
Arron and Cynthia ChenJeff and his bride
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Looking forward2012 has been an eventful year for the groupnew-year resolution
Arron and Cynthia ChenJeff and his bride
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PKPCdiff – PKPDF differential travel time
(Zou et al., 2008)
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Previously proposed mechanisms
A thermochemical F-layerGubbins et al. 2008, GJI
A slurry F-layerInner core freezing must occur above the solid boundary (Loper and Roberts, 1981 PEPI)
CMB
ICB
Slurry zone
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A thermochemical F-layerGubbins et al. 2008, GJI
A slurry F-layerInner core freezing must occur above the solid boundary (Loper and Roberts, 1981 PEPI)
CMB
ICB
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Geodynamics
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Origin of Vp gradientCan solid/liquid fraction account for Vp gradient?