HR: 0800h
AN: P11A-0095    [Abstracts]
TI: The Role of Electron Carriers for Thermal Conductivity in Super-Earth Planets
AU: * Wentzcovitch, R M
EM: wentzcov@cems.umn.edu
AF: University of Minnesota, Dept. of Chemical Engineering and Materials Science, M.S.I. and VLAB, Minneapolis, MN 555455 United States
AU: Yuen, D A
EM: davey@krissy.geo.umn.edu
AF: University of Minnesota, Dept. of Geology and Geophysics, MSI and VLAB, Minneapolis, MN 55455 United States
AU: Umemoto, K
EM: umemoto@cems.umn.edu
AF: University of Minnesota, Dept. of Chemical Engineering and Materials Science, M.S.I. and VLAB, Minneapolis, MN 555455 United States
AU: Allen, P B
EM: phlip.allen@stonybrook.edu
AF: State University of New York, Dept of Physics, Stony Brook, NY 14853 United States
AB: The recent discovery of an extrsolar planet, with 7.5 times the mass of the Earth, has prompted investigation of a new range of parameter space, 3 times hotter and 10 times higher pressure P than that of the Earth's mantle. We estimate thermal conductivity k(T) of silicates and oxides under these extreme planetary conditions. The radiative portion of k(T) is large above the mid-lower post-perovskite mantle, where T reaches 5000-6000K. This stabilizes large plumes because the temperature derivative of k(T) is positive. At T higher than 5000 K, free electron carriers are thermally activated with the population n(T) increasing as exp(-E*/2kT), where E* is the band gap energy of around 5 eV. Free carriers damp electromagnetic waves at frequencies below the plasma frequency, estimated to be close to 1 eV, shutting down radiative heat transport. We find that thermal electrons are highly mobile, with small effective masses and weak scattering. Therefore, they become dominant carriers of heat. We predict electrical resistivity as low as 1000 micro-ohm cm. The activated exponential T-dependence of k(T) will promote the growth of superplumes in the deep post-perovskite mantle of super-earth planets( van den Berg, Beebe, Yuen, Fall AGU abstract, 2005 )
DE: 5430 Interiors (8147)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005