Telluric current

A telluric current (from Latin tellūs 'earth'), or Earth current,^[1] is an electric current that flows underground or through the sea, resulting from natural and human-induced causes. These currents have extremely low frequency and traverse large areas near or at Earth's surface. Earth's crust and mantle are host to telluric currents, with around 32 mechanisms generating them, primarily geomagnetically induced currents caused by changes in Earth's magnetic field due to solar wind interactions with the magnetosphere or solar radiation's effects on the ionosphere. These currents exhibit diurnal patterns, flowing towards the Sun during the day and towards the geomagnetic poles at night.

Both telluric and magnetotelluric methods exploit these currents for subsurface exploration, aiding in activities like geothermal and mineral exploration, petroleum prospecting, fault zone mapping, groundwater assessment, and the study of tectonic plate boundaries. The phenomenon has also captured the imagination of authors, finding its way into fiction. In Umberto Eco's Foucault's Pendulum, the search for a mystic center of the Earth connects to telluric currents, while Thomas Pynchon's Mason & Dixon incorporates them as enigmatic communication conduits alongside Hollow Earth theories.