There is a transfer of heat from the inner solid core to the outer liquid core and it causes the convention of liquid iron of outer core. As iron is metal and it is a good conductor of electricity, so, its motion causes the generation of the magnetic field. The magnetic field of the earth is defined by the north and south pole that generally aligns with the axis of rotation. The lines of magnetic forces are flowing into the earth, in the northern hemisphere and are coming out of the earth in the southern hemisphere.
How Magnetic Field is Produced
Due to the specific shape of field lines, the magnetic forces are trending at different angles, to surface in the different locations. The force is vertical at the north and south pole. But any other position on the equator, it is horizontal. And at any position in between the magnetic force is at some of the intermediate angles to the surface of the earth. The differences in the pressure, temperature, and composition within the outer core cause the various convection currents in the molten metal where there is the sinking of cool dense matter while rising is observed for the warm matter. Due to the flow of liquid iron, an electric current is generated, which, in turn, leads to the production of a magnetic field. Through this field there is passing of charged metals, so they create their electric current, and the cycle is continued.
Electric Current and Magnetic Field
The earth’s magnetic field is generated within the outer core due to the connective movement of liquid iron, but over the geological time, this magnetic field is not stable. The earth’s magnetic field is similar to that of a bar magnet that is titled 11 degrees from the spin of the axis of the earth. As the magnetic fields are surrounding the electric currents, so it can be summarized that the circulating electric currents are in the molten metallic core of the earth, which is the main origin of the metallic field. The magnetic field magnitude at the surface of the earth is half of the Gauss and is sipping towards earth in the northern hemisphere. There is variation in magnitude over the earth’s surface in the range of 0.3-.6 Gauss.
The magnetic field of the earth is attributed to the dynamo effect of the circulating current its direction is not constant. Different specimens of rocks having different ages in the same locations have been reported to have different directions of the permanent magnetization. Additionally, the evidence of 171 different magnetic field reversals during the past years, about 71 million years, have also been reported.
