PROFESSOR BINOD SREENIVASAN

The Earth has a large-scale dipole magnetic field, powered by a convection-driven dynamo in its liquid iron core. In this talk, the possible origin of the Earth's dipole field structure is discussed. The action of the Lorentz force in a rotating dynamo may be such that a dipole is preferred over a quadrupole, or a field of any other polarity. Today's geomagnetic field is also made up of 4 high-latitude lobes of concentrated flux symmetrically placed north and south of the equator. They have not moved much during the historical period of direct observation. We examine the dynamo regime conducive to the generation of these lobes. Finally, we look at the polar regions, where the magnetic field is relatively weak, and sometimes reversed in sign.