Numerical Modeling of Magnetic Field Due to Marine Currents in the Strait of Hormuz

Summary The Strait of Hormuz is a narrow waterway, which restricts water exchange between the Persian Gulf with the Gulf of Oman. This strait is exposed to inflow of Indian Ocean surface water and outflow of saline bottom water formed in the Persian Gulf. This water exchange leads to magnetic anomaly, which affects the
measured geo-magnetic field. In this research work, first, the marine currents in the Strait of Hormuz have been simulated using MIKE21 numerical model. Then, using extracted currents and appropriate relations the induced magnetic field due to marine currents has been calculated. The results show the space and temporal variability of current induced magnetic field in the study region. According to the study results, the maximum amount of vertical component of magnetic field in the study region varies between 0 to137 nT, while this amount for horizontal component of magnetic field varies between 0 to 153 nT.
Introduction Todays the applications of marine geo-magnetic field have been increased in several fields such as marine navigation, subsurface detection, etc. These applications cause to focus on the natural factors, which have direct impacts on marine geo-magnetic field. Among these natural factors, ocean or marine currents play a specific role on electromagnetic induction, and thus, influence ocean induced magnetic field, because of high electrical conductivity of marine waters and the dynamic impact of ocean currents. In the Iranian water, the Strait of Hormuz plays an important role on the magnetic field due to marine currents because of its complex regime of currents and its specific location. Therefore, this region has been selected for this study.
Methodology and Approaches In this research, the bathymetry map of study region has been obtained from GEBCO Database. Then, grid generation and interpolation of these data have been carried out using the mesh generation subroutine of MIKE21-MIKE ZERO software package. This mesh has been produced for introducing of geometry and bathymetry problems and includes irregular triangle elements. The final mesh, which has been used in this model, includes 49819 elements and 27915 nodes. In the produced model of the region, there are two open water boundaries at west and east of the Strait of Hormuz and two dry boundaries at south and north of the Strait. The required information for these boundaries has been forced to the model in the form of a data file, in which the data varies with time and space along the boundaries. The boundaries information is in format of P and Q parameters, which introduce the eastward and northward components of flow. After implementation of the model, for calculating the components of current induced magnetic field we use the model output data of flow and related formulation between components of magnetic field and components of flow.
Results and Conclusions According to the study results, the maximum amount of vertical component of magnetic field in the study region varies between 0 to137 nT, while this amount for horizontal component of magnetic field varies between 0 to 153 nT. In general, we can conclude that two factors of surface currents velocity and subsurface volume flow rate are the major factors influencing the magnetic field oscillations in the study region.