HR: 17:00h
AN: GP12B-05    [PDF]
TI: Geomagnetic induction modelling based on CHAMP magnetic vector data
AU: * Martinec, Z
EM: zdenek@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: McCreadie, H
EM: bilby@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AB: The first results of modelling geomagnetic induction signals induced by equatorial ring currents in the magnetosphere recorded at satellite altitudes, are presented. The input of the model consists of the $X$-component of the magnetic induction vector measured by the CHAMP vector magnetometer along individual night-time satellite tracks. The magnetic induction signals measured along day-time tracks and above polar regions are not considered because they are disturbed by signals with sources different from ring currents. Thus, only mid-latitudes are considered. Only periods during magnetic storms with time scales of the order of days are analysed because the induced signal is most intense. Forward modelling of magnetic induction is implemented in the time domain using the spectral-finite element method developed by Martinec et al. (2003) and recently modified for satellite data. The output is the $Z$-component of the magnetic induction vector at satellite altitudes. We test the sensitivity of the computed $Z$-component using an electrical conductivity model for the Earth's mantle. We then compare the output with CHAMP magnetic data and evaluate the acceptability of the electrical conductivity model adopted. We show that a spherically symmetric model of electrical conductivity is too restrictive to adjust to the $Z$-component of the CHAMP magnetic data for all night-time, mid-latitude satellite tracks over a magnetic storm. For near-future considerations, this implies the necessity to introduce a more complex conductivity structure of the Earth's mantle when interpreting the CHAMP magnetic induction data. Martinec, Z., M. E. Everett and J. Vel\'\i msk\'y, 2003. Time-domain, spectral-finite element approach to transient two-dimensional geomagnetic induction in a spherical heterogeneous earth, {\it Geophys. J. Int.}, (in press).
DE: 1515 Geomagnetic induction
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting