Analysis of the natural electric field at different sea depths

Abstract

The natural electric field at the depth of 0 ∼ 1500 m in high seas of South China Sea is obtained by using a new type of measuring device. The electric field data in the 0.01 ∼ 0.5 Hz and 0.5 ∼ 30 Hz frequency range are analyzed respectively. The results show that the induced electric field generated by the surface wave (about 0.14 Hz in the experiment) is obvious at the depth of 50 m but can be ignored at the depth greater than 100 m. When the depth increases from 50 m to 1500 m, the peak-to-peak value of the natural electric field gradually decreases. At the depth of 1000 m, the peak-to-peak values are 0.04 ∼ 0.08 μV/m in the 0.01 ∼ 0.5 Hz range, and 0.07 ∼ 0.1 μV/m in the 0.5 ∼ 30 Hz range. At last, the natural electric field in coastal water near Sanya City, where the water depth is 15 m, is measured by means of a sinking device. The results show that the peak-to-peak values are about 2 ∼ 4 μV/m in the 0.01 ∼ 0.5 Hz range and 2 μV/m in the 0.5 ∼ 30 Hz range. By comparing the natural electric field in high seas with that of coastal water, we find the latter has a larger peak-to-peak value at nearly the same water depth. In addition, line spectrum noise often occurs in coastal water, while it is rarely observed in high seas when the water depth is more than 50 m.