ELF propagation in deep and shallow sea water
Abstract
In this paper, electromagnetic wave propagation at Extremely Low Frequencies (ELF) in deep and shallow sea water is considered. The term 'ELF' is used here somewhat loosely to refer to the frequency band 0-3 kHz. The radiation source is considered to be located in the sea water and is taken to be a horizontal electric dipole (HED) or a vertical electric dipole (VED). For the deep water ease, a comparison is made between results computed using complex image theory and results calculated using the full Sommerfeld integral formulation. Both of these formulations include the lateral waves which propagate along the air-sea interface. Moving on to the case of shallow water, there are two lateral wave modes of propagation-lateral waves which propagate on the sea surface and along the seabed. These modes are included by numerical evaluation of the Sommerfeld integrals which appear in the complete solution. We also compare the relative efficacy of subsurface horizontal electric dipoles and vertical electric dipoles as radiators. For the case of zero frequency (dc), the Sommerfeld integrals simplify considerably enabling the fields to be evaluated as the sums of infinite series. This dc formulation leads to much reduced computation time. Finally, the effects on propagation of long-wavelength water gravity waves or tides on the surface of the sea are examined by considering these waves as a perturbation to the sea-air interface.
- Publication:
-
In AGARD
- Pub Date:
- May 1993
- Bibcode:
- 1993rpsa.agarU....B
- Keywords:
-
- Deep Water;
- Electric Dipoles;
- Electromagnetic Wave Transmission;
- Extremely Low Frequencies;
- Perturbation;
- Radiation Sources;
- Shallow Water;
- Gravity Waves;
- Ocean Bottom;
- Ocean Surface;
- Sea Water;
- Water Waves;
- Communications and Radar