Unit of the Earth's magnetic field. 1 Gamma equal to 1 nanotesla equal to 10 Gauss. Top

It is an electromagnetic radiation carried out by high energy photons (energies in excess of 100 keV or frequency of greater than 1E19 Hz). Gamma rays are observed during large, extremely energetic solar flares. It is a very dangerous radiation because of its large capacity to ionize. Shielding gamma rays requires large amounts of mass, like bodies with high densities or very thick. Top

Is a mathematical model of the general circulation of a planetary atmosphere or ocean and based on the Navier-Stokes equations on a rotating sphere with thermodynamic terms for various energy sources (radiation, latent heat). Top

They are two points, the north pole and the south pole, on the surface of a rotating planet (or other rotating body) where the axis of rotation meets the surface of the body. Top

Natural variations in the geomagnetic field classified into quiet, unsettled, active and storm conditions. Descriptive levels of activity such as these are determined by the A index defined as follows: A minor 8 - "quiet"; 8 minor or equal to A minor or equal to 15 - "unsettled"; 16 minor or equal to A minor or equal to 24 - "active"; 25 minor or equal to A minor or equal to 35 - "minor storm"; A major or equal to 36 upwards - "major storm". Top

Where the geomagnetic field is horizontal to the Earth and the inclination is zero. Top

Corresponds to the magnetic field observed in and around the Earth. Top

A near-DC current which can flow in grounded conductors as a result of surface electric fields arising from the energized currents and associated time-varying magnetic fields in the ionosphere. Ultimately, GIC are driven by magnetic storms and substorms. Top

A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a solar wind shock wave which, typically, strikes the Earth's magnetic field 24 to 36 hours after the event, associated with solar structures. Top

Elevation above Earth’s surface. Top

It is a discipline of science which uses the tools of mathematics and physics to answer questions about the Earth. Top

The potential of the Earth's gravity field. It is defined as the work per unit mass done against the gravity for to elevate an object from sea mean level to a determinate height above this level. Top

Vertical coordinate referenced to Earth's mean sea level. An adjustment to geometric height using the variation of gravity with latitude and altitude. It can be considered as gravity-adjusted height. It is defined as ratio between the geopotential in determinate height and the gravity value on the sea mean level. Top

Orbit that which a body maintain a constant position relative to Earth’s surface. Top

Satellite which describes a geostationary orbit. Top

It is a wind resulting from balance between Coriolis and pressure gradient forces. Top

It is a satellite which describes a geosyncronous orbit. Top

It Is a geocentric orbit that has the same orbital period as the sidereal rotation period of the Earth. Top

Giga is a prefix which denotes 1E9. Top

Model used to explain the difference in potential which exists between the Earth's surface and ionosphere, and steady flow of electrons Top

It is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. Top

It is a radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces. It is an alternative and complementary to the United States' GPS, the Chinese Compass navigation system, and the planned Galileo positioning system of the European Union (EU). Top

System set of satellite which provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather conditions, day and night, anywhere near the Earth. Top

Consist of satellites in semisynchronous (12-hour) orbits launched into six different orbital planes each tipped 55 degrees with respect to the equator. Top

It is a kind of RO technique used to obtain the parameters of the atmosphere. In the GPS RO the radio wave is emitted from one of the GNSS satellites, pass a fraction of atmosphere, undergoing refraction, and because of the bending, arrives on the receiver equipment, behind the limb. Top

A rate of change with respect to distance of a variable quantity, as temperature or pressure, in the direction of maximum change. The gradient is a vector operator denoted and sometimes also called Del or nabla. Top

Granules on the photosphere of the Sun are caused by convection currents (thermal columns, Benard cells) of plasma within the Sun's convective zone. The grainy appearance of the solar photosphere is produced by the tops of these convective cells and is called granulation. Top

A fluid wave that has gravity as its primary restoring force (as opposed to vertical pressure gradient). Top

They are vertically propagating waves associated with the bouyancy restoring force in stably stratified fluids. Top

Atmospheric heating caused by solar radiation being readily transmitted inward through the Earth's atmosphere but long wave radiation less readily transmitted outward, due to absorption by certain gases in the atmosphere. Top

SEE Universal Time. Top

The radio wave which propagates close to the Earth's surface. Severe signal losses due to ground resistance limit the range of ground waves to about 100 km over land and 300 km over sea for the lowest HF frequencies. The ground waves for the higher HF frequencies cover much shorter distances. Top

It is a sudden increase in the cosmic ray intensity recorded by ground based detectors. GLE is invariably associated with large solar flares but the acceleration mechanism producing particles of up to tens of GeV is not understood. Top