Earth's magnetic field generated by convection of liquid iron in the outer core (geodynamo)
extends from the core through the mantle, crust, and out into space as the magnetosphere
deflects solar wind and charged particles, protecting the atmosphere from erosion
the magnetosphere channels particles to the poles, creating auroras
enables navigation: compass alignment with magnetic north used for millennia
magnetic poles wander and periodically reverse (last reversal ~780,000 years ago)
paleomagnetism in rocks provided key evidence for plate tectonics and seafloor spreading
shields surface life from cosmic radiation, a prerequisite for biological evolution
field strength has decreased ~9% over the last 200 years
the South Atlantic Anomaly is a region of weakened field affecting satellites
connected to energy dynamics of the planetary interior through thermodynamics