Earth’s Magnetic Field
The Earth’s magnetic field is generated by the geodynamo process within the Liquid Outer Core, where convective motion of electrically conducting iron-nickel alloy creates electric currents. It extends from the core to space, forming the Magnetosphere, which shields the planet from Solar Wind and cosmic-rays.
Key Characteristics
- Dipole Nature: Approximates a tilted magnetic dipole, with magnetic poles offset from geographic poles.
- Variability: Subject to secular variation, magnetic excursions, and full Geomagnetic Reversals over geological timescales.
- Intensity: Averages ~25 to 65 microteslas (µT) at the surface.
Geological Significance
- Paleomagnetism: Magnetic minerals in cooling lava record the field’s direction and intensity, serving as a primary tool for reconstructing Continental Drift and tectonic-plate movements.
Biological Interaction
- Magnetoreception: Certain species exhibit sensitivity to geomagnetic fields for navigation. Recent studies suggest this may be mediated by superparamagnetic iron oxide nanoparticles within macrophages in organs such as the liver and spleen, rather than solely through cryptochromes in the eyes. See Pigeon Navigation: Superparamagnetic Macrophages in Liver and Spleen Explain Earth’s Magnetic Field Sensing.