Geomagnetics: a branch of geophysics concerned with all aspects of the Earth's magnetic field which is produced in the inner core. This includes its origin, variation through time, and manifestations in the form of magnetic poles, the remanent magnetization of rocks, and local or regional magnetic anomalies.The Earth's magnetic field is predominantly a geo-axial dipole, with north and south magnetic poles located near the geographic poles that undergo periodic reversals and excursions.