HR: 0800h
AN: GP31A-0069    [Abstracts]
TI: Isolating Magnetospheric Contributions for Electromagnetic Induction Studies Using Satellite Data
AU: * Richmond, N C
EM: nic@ucsd.edu
AF: IGPP, Scripps Institution of Oceanography, University of California, San Diego 9500 Gilman Drive, La Jolla, Ca 92092-0225 United States
AU: Ribaudo, J
EM: jribaudo@UCSD.Edu
AF: IGPP, Scripps Institution of Oceanography, University of California, San Diego 9500 Gilman Drive, La Jolla, Ca 92092-0225 United States
AU: Constable, C
EM: cconstable@UCSD.Edu
AF: IGPP, Scripps Institution of Oceanography, University of California, San Diego 9500 Gilman Drive, La Jolla, Ca 92092-0225 United States
AU: Constable, S C
EM: sconstable@UCSD.Edu
AF: IGPP, Scripps Institution of Oceanography, University of California, San Diego 9500 Gilman Drive, La Jolla, Ca 92092-0225 United States
AB: Previous satellite induction studies have used vector or scalar satellite magnetometer data to infer the electrical conductivity of the mantle. The approach uses existing field models (e.g. OSVM, CM4) to remove core, ionospheric, lithospheric and time invariant magnetospheric sources, and isolate variations due to the magnetospheric ring current. Internal and external contributions can be estimated for each equatorial satellite pass, and these time series are used to determine frequency dependent response functions that are inverted for electrical conductivity profiles for the mantle. We report on our progress in analyzing Ørsted data, and on an assessment of the relative merits of vector or scalar data for induction studies. For 1999-2002 data we use the CM4 comprehensive magnetic field model to remove unwanted field contributions, in the later part we merge an updated model for the core field and secular variation with the remainder of the corrections supplied by CM4. An estimate of Dst derived directly from Ørsted data is in good agreement with the Dst index, indicating a general ability to isolate fields due to the time varying magnetospheric sources for local times sampled by Ørsted. Ørsted has sampled the full range of sun times since it was launched in 1999, so results obtained for different local times provide insight into the ability of current field models to represent ionospheric sources and highlight the effects of including different field components in the estimation of satellite Dst. A synthetic analysis based on scalar Magsat data yields internal and external coefficients in good agreement with those determined from the vector data. More realistic noise models are investigated to determine the limitations of using scalar data in satellite induction studies.
DE: 1515 Geomagnetic induction
DE: 1541 Satellite magnetics: main field, crustal field, external field
DE: 2778 Ring current
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005