Frequency response of the transfer functions of the current channelling between two oceans.

Abstract

Several current channelling models between two oceans are presented for studying the frequency responses of the transfer functions and the anomalous horizontal magnetic field in the ‘E-polarization’ case (i. e., the inducing magnetic field is perpendicular to the direction of the channel). The results obtained from this numerical investigation give support to the idea that at longer periods, the lack of frequency dependence of the transfer functions and the anomalous horizontal magnetic field is the characteristic consequence of the channelling effect of the oceanic induced currents. On the contrary, the corresponding 2-D local induction models show that the frequency responses of the transfer functions and the anomalous horizontal field are quite sensitive to the period of the inducing field at the longer periods. When there is no highly conducting layer lying under the surface structure, we have found another property which arises from the channelling effect of the oceanic induced currents; that is, the vertical magnetic component is nearly in-phase with the normal magnetic field. Likewise, the horizontal component of the anomalous magnetic field will also be nearly in-phase with the normal field. However, when a conducting layer exists below the ocean and its buried depth is not very deep, the in-phase properties stated above no longer hold. Furthermore, we investigate the behaviour of the oceanic current in a channelling model for the ‘B-polarization’ case (i. e., the inducing magnetic field is parallel to the channel) at one period, T=10000s. The result also shows that the anomalous magnetic field is nearly in-phase with the normal magnetic field, provided that no highly conducting layer lies under the surface structure.