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

2. Collaborators Advanced Photon Source 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

3. Seismic features of the F-layer Outer Core Inner Core F-layer PRE M AK13 5 PREM2 Zou et al. 08 Krasnoshchekov et al. 05 Cao et al. 07 Sun and Song 08 Gubbins et al. 08,

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

5. Occurrence of “snowfall” in Earth’s core ? Case 1Case 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 =  thT/K liq  th: 1.65 K liq: 1343 T: geotherm Perturbation to geotherm Dziewonski and Anderson 81 Anderson O. 98 Greff-Lefftz and Legros 99,

8. Melting curve Lindemann’s Law for fixed composition dT m /dP = 2(  SL – 1/3)T m /K sol 2(  SL – 1/3) = K’ -1, K’ = 1.7 to 3.6 K sol: 1500 T m : 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: Greff-Lefftz and Legros 99, Temperature near ICB increases due to resonant period and viscomagnetic friction power

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. PKP Cdiff – PKP DF differential travel time (Zou et al., 2008)

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

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

20. Geodynamics

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