The Earth's geomagnetic field

1. Main Field:
The main field accounts for the largest part of the observed field. Its origin lies deep in the interior of the Earth: It is caused by a geodynamo-process in the Earth's outer core and changes slowly (secular variation).

2. Crustel Magnetic Field (Lithospheric Field):
This field is irregular (local anomalies) and much smaller than the main field. Its sources lie in the upper crust of the Earth.

3. External Fields:
The external field , also much smaller than the main field, is caused by current systems outside the Earth. It is subject to significant variations due to the influence of solar irradiation and the solar wind.

Declination (D): Angle between geographic North direction and magnetic North direction, eastward positive. North Component (X): Strength of the magnetic field parallel to the Earth's surface toward geographic North. East Component (Y):Strength of the magnetic field parallel to the Earth's surface toward geographic East. Horizontal Intensity (H): Strength of the magnetic field parallel to the Earth's surface toward magnetic North. Vertical Intensity (Z): Strength of the magnetic field vertical to the Earth's surface, positive down. Inclination (I): Angle towards the Earth's surface, positive down. Total Intensity (F): Total strength in the magnetic field direction.