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“Snowfall” in F Layer

“Snowfall” in F Layer. CIDER Post-AGU 2012. 2:57 PM, Dec. 8 , 2012 . Jie (Jackie) Li University of Michigan. Advanced Photon Source. Collaborators. Jeffrey Pigott – Mineral Physics (Ohio State) Jie (Jackie) Li – Mineral Physics (U of Michigan)

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“Snowfall” in F Layer

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  1. “Snowfall” in F Layer CIDER Post-AGU 2012 2:57 PM, Dec. 8, 2012 Jie (Jackie) Li University of Michigan Advanced Photon Source

  2. 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 Advanced Photon Source

  3. Seismic features of the F-layer PREM AK135 PREM2 Outer Core F-layer Zou et al. 08 Krasnoshchekov et al. 05 Cao et al. 07 Sun and Song 08 Gubbins et al. 08 Inner Core ,

  4. “Snowing” cores in Solar System Stewart et al. 07 Science Chen et al. 08 GRL Williams 09 Hauck et al. 06 JGR

  5. Occurrence of “snowfall” in Earth’s core? Case 1 Case 2 Case 1 Melting gradient decreases Case 2 Adiabatic gradient increases

  6. Integrative approach MP - 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

  7. Adiabatic temperature gradient Core adiabat (dT/dP)S = gth•T/Kliq gth: 1.65 Kliq: 1343 T: geotherm Perturbation to geotherm Anderson O. 98 Dziewonski and Anderson 81 Greff-Lefftz and Legros 99,

  8. Melting curve Lindemann’s Law for fixed composition dTm/dP = 2(gSL – 1/3)•Tm/Ksol 2(gSL – 1/3) = K’ -1, K’ = 1.7 to 3.6 Ksol: 1500 Tm: melting temperature Binary solution Dziewonski and Anderson 81 Seagle et al. 09

  9. Grüneisen parameters

  10. Case 1a: Wide “Snowing zone” Parameter space for “snowing”

  11. Case 1b: Narrow “snowing” zone Chen et al. 08

  12. Case 2: Temperature near ICB increases due to resonant period and viscomagnetic friction power Greff-Lefftz and Legros 99,

  13. 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

  14. Tips and Traps Accomplishments - 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

  15. Looking forward 2012 has been an eventful year for the group new-year resolution Arron and Cynthia Chen Jeff and his bride

  16. Looking forward 2012 has been an eventful year for the group new-year resolution Arron and Cynthia Chen Jeff and his bride

  17. PKPCdiff – PKPDF differential travel time (Zou et al., 2008)

  18. CMB ICB Previously proposed mechanisms Slurry zone A slurry F-layer Inner core freezing must occur above the solid boundary (Loper and Roberts, 1981 PEPI) A thermochemical F-layer Gubbins et al. 2008, GJI

  19. CMB ICB A slurry F-layer Inner core freezing must occur above the solid boundary (Loper and Roberts, 1981 PEPI) A thermochemical F-layer Gubbins et al. 2008, GJI

  20. Geodynamics

  21. Origin of Vp gradient • Can solid/liquid fraction account for Vp gradient?

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