Earth's magnetic field

The Earth's magnetic field is generated by electric currents in both the deep interior and high above the surface of the planet. The field extends far into interplanetary space where it encounters the moving plasma of the solar wind that flows around the magnetic field, compressing it on the dayside and stretching it out into a long tail on the night side.

The geomagnetic field shields the Earth's surface from high energy particles emitted from the sun, and the solar wind, by deflecting them around earth. During magnetic storms vast amounts of energy from the sun are dumped into the earth's upper atmosphere affecting satellites, electricity supplies, radio communication and producing expanded auroral displays.

Diagram of the seven components of the magnetic vector

As the earth's magnetic field is a vector quantity it has a direction and an intensity that can be described by combinations of components or "elements". In geomagnetism the elements most commonly referred to are X, Y, Z, F, H, D and I as shown in the diagram.

A compass needle points to magnetic north, which is defined by the direction of the horizontal component of the geomagnetic field (H). The geomagnetic declination (D), sometimes called variation, is the angle between true north and magnetic north.

The inclination (I), sometimes called dip, is the angle the field vector is inclined to the horizontal plane.

Geomagnetic observatories in Australia monitor four of the elements of the geomagnetic field, the true north (X component), true east (Y component), vertical (Z component) and the total intensity of the magnetic field (F).

The X, Y, Z, F and H intensity elements of the magnetic field are measured in units of nanotesla (nT). Declination (D) and the inclination (I) are measured in angular degrees.

All other elements of the magnetic field can be derived from X, Y and Z. For example, F is calculated using the following equation

More information about the components of the magnetic field.

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