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Radio Science

ULF/ELF magnetic fields generated at the sea surface by submerged magnetic dipoles


  • A. C. Fraser-Smith,

  • D. M. Bubenik


The complete expressions for the electromagnetic fields generated by buried harmonic dipole sources involve complex integrals that cannot ordinarily be solved in closed form. We present numerical solutions for the quasi-static magnetic fields at the sea surface due to magnetic dipoles submerged from 25 m to 200 m in an infinitely deep sea, for frequencies in the interval 0.1 Hz to 100 Hz. We also present the ratios of the calculated fields to the fields which would be observed if the source were in unbounded free space. It is shown that the presence of the conducting sea water may enhance the field amplitudes in some cases. The results support the commonly proposed “up and over” propagation mechanism for the distant fields from a submerged dipole source.

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