non-dipole field

The Earth's magnetic field is primarily dipolar, meaning it resembles that of a bar magnet. This dipolar field accounts for over 90 percent of the observed magnetic field. However, there are deviations from this ideal dipole, known as the non-dipole field or regional geomagnetic anomalies.12

The non-dipole field is weaker than the main dipolar field and is thought to originate in the Earth's outer core. These anomalies can affect compass readings, particularly in polar regions, and influence particles trapped in the Earth's outer field. While the dipolar field is the dominant component, the non-dipole field represents irregularities that are crucial for a more complete understanding of Earth's magnetic behavior.21