“snowfall” in f layer
Post on 24-Feb-2016
56 Views
Preview:
DESCRIPTION
TRANSCRIPT
2:57 PM, Dec. 8, 2012
CIDER Post-AGU 2012
“Snowfall” in F Layer
Jie (Jackie) LiUniversity of Michigan
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
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,
“Snowing” cores in Solar System
Williams 09 Hauck et al. 06 JGRChen et al. 08 GRL
Stewart et al. 07 Science
Occurrence of “snowfall” in Earth’s core?Case 1
Case 2
Case 1Melting gradient
decreases
Case 2Adiabatic gradient
increases
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
Adiabatic temperature gradient
Core adiabat(dT/dP)S = gth•T/Kliqgth: 1.65Kliq: 1343T: geotherm
Perturbation to geotherm
Dziewonski and Anderson 81Anderson O. 98
Greff-Lefftz and Legros 99,
Melting curveLindemann’s Law for fixed compositiondTm/dP = 2(gSL – 1/3)•Tm/Ksol2(gSL – 1/3) = K’ -1, K’ = 1.7 to 3.6Ksol: 1500Tm: melting temperature
Binary solution
Dziewonski and Anderson 81
Seagle et al. 09
Grüneisen parameters
Case 1a: Wide “Snowing zone”Parameter space for “snowing”
Case 1b: Narrow “snowing” zone
Chen et al. 08
Case 2:
Greff-Lefftz and Legros 99,
Temperature near ICBincreases due to resonant period and viscomagnetic friction power
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
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
Looking forward2012 has been an eventful year for the groupnew-year resolution
Arron and Cynthia ChenJeff and his bride
Looking forward2012 has been an eventful year for the groupnew-year resolution
Arron and Cynthia ChenJeff and his bride
PKPCdiff – PKPDF differential travel time
(Zou et al., 2008)
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
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
Geodynamics
Origin of Vp gradientCan solid/liquid fraction account for Vp gradient?
top related