Earth Planets Space, Vol. 58 (No. 4), pp. 429-437, 2006
C. Manoj 1,2, A. Kuvshinov3,4, S. Maus1,5, and H. Lühr1
2National Geophysical Research Institute, Hyderabad, India
3Danish National Space Center, Copenhagen, 2100, Denmark
4Geoelectromagnetic Research Institute, Troitsk, Russia
5NOAA's National Geophysical Data Center, Boulder, U.S.A.
(Received November 15, 2004; Revised March 29, 2005; Accepted April 21, 2005; Online published April 14, 2006)
Conducting ocean water, as it flows through the Earth's magnetic field, generates secondary electric and mag-netic fields. An assessment of the ocean-generated magnetic fields and their detectability may be of impor-tance for geomagnetism and oceanography. Motivated by the clear identification of ocean tidal signatures in the CHAMP magnetic field data we estimate the ocean magnetic signals of steady flow using a global 3-D EM nu-merical solution. The required velocity data are from the ECCO ocean circulation experiment and alternatively from the OCCAM model for higher resolution. We assume an Earth's conductivity model with a surface thin shell of variable conductance with a realistic 1D mantle underneath. Simulations using both models predict an amplitude range of ±2 nT at Swarm altitude (430 km). However at sea level, the higher resolution simulation predicts a higher strength of the magnetic field, as compared to the ECCO simulation. Besides the expected signatures of the global circulation patterns, we find significant seasonal variability of ocean magnetic signals in the Indian and Western Pacific Oceans. Compared to seasonal variation, interannual variations produce weaker signals.
Key words: Ocean flow, geomagnetic field, satellite measurements.