Earth's Magnetic Field: Geodynamo, Reversals, and Navigation

Status: draft · Confidence: low (0.45) · Basis: verified_sources

Quality notes: placeholder_content, generic_source_homepage, no_verified_sources, partial_source_verification

## TL;DR

Earth's magnetic field: geodynamo in liquid iron outer core. Surface strength 25-65 μT. Poles wander 10-50 km/year. Reversals every 200,000-300,000 yr avg (last 780,000 yr ago). South Atlantic Anomaly: field 30-50% weaker, satellite hazard.

## Core Explanation

Structure: 95% dipole (tilted 11°). Reversals recorded in seafloor magnetic stripes. Brunhes-Matuyama reversal 780,000 years ago. Laschamp excursion ~41,000 years ago. Field weakening ~5%/century. Animal magnetoreception: cryptochrome in birds, magnetic map in sea turtles. ESA Swarm mission (3 satellites, 2013-present).

## Detailed Analysis

[待后续补充。]

## Further Reading

- [Source 1 — Earth's Magnetic Field: Geodynamo, Reversals, and Navigation](https://www.ncei.noaa.gov/)

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