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Ionosphere

With two frequencies ionosphere as a dispersive medium influences the ray paths of GNSS satellites to a receiver. If all positions are known the delays can be used to compute the integrated field strength of the electrical atmosphere. The typical parameter is called TEC (Total Electron Content). For mapping the vertical TEC VTEC is used by applying a mapping function to the observed slant delays. A regular global service from CODE (Berne, Switzerland) uses stations to produce a (2.5°x2.5°x2h).

The figure on the left shows the differences caused by choosing a different station set.

Under quiet circumstances the differences are near zero and show some spots where there are no stations.The main investigation is done with extreme events (geomagnetic storms, travelling disturbances). The TEC values increase dramatically (200% and more) within hours and may cause damage to electrical equipment. Quick detection of this changes and early warnings can reduce the damage by switching off sensitive equipment (satellites, power plants, transmitters).

Geographical distribution of a geomagnetic storm of 2005 for a certain hour.
Last update: 07/19/11
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