Calculation of the electromagnetic fields generated by DC horizontal current element in semi-infinite space of seawater

Ship is constructed by steel and induces electromagnetic field when ship moves across the Earth's magnetic field. This electromagnetic field is very important object characteristic of ship. In this paper, a simple method is proposed, the electromagnetic field expressions in seawater for DC horizontal current element located in air half-space and immersed in seawater half-space respectively are derived by using the classical Sommerfeld Hertz vector. The method is simpler than Wait's and Bannister's. This study is theoretical basis of further research on the electromagnetic field of ship moving across the geomagnetic field in seawater.