Relating to the magnetic properties (geomagnetism) of the Earth: A geomagnetic study involves the sources, configurations, and changes in the Earth's magnetic field. It includes the interpretation of the remaining magnetism in rocks as a result of the Earth's magnetic field at the time when the rocks were formed, which is known as "paleomagnetism".

In geophysics, the minimum energy of a cosmic-ray particle which can reach the top of the atmosphere at a specified or at a particular geomagnetic latitude: Mr. Sky asked his students if a geomagnetic cutoff referred to the maximum energy or to the lowest energy level of a highly penetrating ionising radiating element of an extraterrestrial origin that would be able to reach the upper part of the atmosphere.

The dipole or a pair of equal and opposite electric charges or magnetic poles that are separated by a short distance: A geomagnetic dipole is created by the Earth's magnetic field.

An instrument that can be suspended from the side of a moving ship to measure and to calculate the direction and speed of ocean currents: A geomagnetic electrokinetograph is used while the ship is underway by measuring the voltage produced by the Earth's magnetic field in the moving conductive seawater.

The components of the geomagnetic field at the surface of the Earth: The different components in the geomagnetism of the world, called geomagnetic elements, and are located on the exterior part of the Earth.

In geophysics, the imaginary great circle on the Earth's surface formed by the intersection of a plane passing through the Earth's center perpendicular to the axis connecting the north and south magnetic poles: The geomagnetic equator is that terrestrial great circle which is 90° from the geomagnetic poles.

The lines of force encvircling a permanent magnet or a moving charged element: The magnetic field is present in and around the Earth.

The intensity of the magnetic field at the Earth's surface is approximately 0.32 gauss at the equator and 0.62 gauss at the north pole.

A "gauss" is equivalent to 1 maxwell per square centimeter, and a "Maxwell" is equivalent to the flux that produces one abvolt in a one-turn circuit when the flux is reduced to zero at a uniform rate in one second, while a "flux" is the electric or magnetic field lines of force that traverse a given cross-sectional area.

Any interference in radio communications caused by terrestrial magnetism or the Earth's magnetic field: Geomagnetic noises are unwanted radio frequencies that are caused by fluctuations in the geomagnetic field of the Earth.

Either of two antipodal (opposite) points marking the intersection of the Earth's surface with the extended axis of a powerful magnet bar which is assumed to be located at the center of the Earth and indicating the source of the actual magnetic field of the Earth: A geomagnetic pole is one of two regions of the Earth with very high magnetic field strength, taken to be the points at which a line, drawn between the poles of a magnetic dipole generating the Earth's magnetic field and extending out in both directions, would cross the Earth's surface.

The north pole of a magnet, such as a compass needle, is attracted to the geomagnetic north pole because the Earth's north pole is actually a magnetic south pole (and its geomagnetic south pole is a magnetic north pole).

Alternation of the Earth's magnetic polarity or a reversal of the polarity of the Earth's magnetic field which has occurred in the past as shown by the remanent magnetization found in igneous and sedimentary rocks: The Earth's internal geomagnetic field reversal changes, on average, about every 300,000 to 1 million years.

This geomagnetic reversal is very sudden on a geologic time scale, apparently taking about 5,000 years.

The time between reversals is highly variable, sometimes less than 40,000 years and at other times as long as 35 million years and no regularities or period times have been discovered so far.

A long interval of one polarity may be followed by a short interval of an opposite polarity.

In geophysics, the changes in the Earth's magnetic field: Such geomagnetic secular variations occur over hundreds of years and are caused by internal changes in the Earth or a variation of any field or parameter which occurs over hundreds of years.

A world-wide disruption of the Earth's magnetic field, distinct from regular diurnal variations: A geomagnetic storm is caused by ionic disturbances from solar events.

Any change that happens to the geomagnetic field: A geomagnetic variation can be temporal or short-time changes in the geomagnetic field, both long-term (secular) and short-term (transient).