HR: 13:55h
AN: GP33A-02 INVITED     [Abstracts]
TI: Quiet Time Contributions to the Geomagnetic Field as Seen in CHAMP, Oersted and SAC-C Satellite Magnetic Measurements
AU: * Maus, S
EM: stefan.maus@noaa.gov
AF: CIRES, University of Colorado, and NOAA's National Geophysical Data Center, 325 Broadway, Boulder, CO 80305 United States
AU: Luehr, H
EM: hluehr@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AB: The continuing satellite magnetic missions CHAMP, {\O}rsted and SAC-C enable us to model the internal geomagnetic field, its secular variation and acceleration to steadily increasing spherical harmonic degrees. Without regularization, the present limits stand at degree 80 for the static and degree 12 for the temporal derivatives. In order to reach and extend these limits, even minor contributions to the magnetic field have to be taken into account. These contributions from the ocean tides, ionospheric currents, ambient plasma, and the magnetosphere are interesting as such and will be discussed and illustrated here. For the latest NGDC/GFZ main field models, CHAMP data are first corrected for a time varying mis-alignment of the vector magnetometer orientation. Accounting for the magnetic pressure of the ambient plasma, the diamagnetic effect is estimated from the electron density and temperature given by CHAMP's Langmuir Probe. Ocean tidal fields are accounted for using the predictions by Kuvshinov of the induced electromagnetic signal, based on the TPXO tidal ocean flow model. External and induced ring current fields are represented by the new Est/Ist index pair. These indices result from splitting the magnetic disturbance field index Dst into an external and internal part for a 1D conductivity model of the Earth. The final model is estimated in two steps: First, a stable ring current field in SM and a degree-2 magnetospheric field in GSM coordinates are determined from a combined satellite data set with 24h local time coverage. After subtracting this external field, the internal field and its temporal derivatives are estimated from night side data only.
DE: 2443 Midlatitude ionosphere
DE: 2467 Plasma temperature and density
DE: 1515 Geomagnetic induction
DE: 1532 Reference fields (regional, global)
DE: 1555 Time variations--diurnal to secular
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting