**Corrected geomagnetic co-ordinates** were introduced by *B.Hultquist and Gustafsson *[1960].

According to *K. Stasiewicz* [1991] the classical algorithm of the **corrected co-ordinates** calculation looks as follows:

- Step 1: The magnetic field line tracing from the satellite position up to magnetic equatorial plane using IGRF magnetic field model.
- Step 2: Tracing back from the point (produced on the Step 1) to the Ionosphere (by using only dipole magnetic field)
- The
**CORLAT**,**CORLON**, and**CORMLT**of the original point are equal to the dipole latitude, longitude and local time of the point, produced on the step 2. - Corrected geomagnetic co-latitude is the difference: (90 deg - CORLAT).

But this algorithm can be used only for the points belonging to the Earth's surface or to the near Earth space limited by 6 RE, where influence of the extraterrestrial magnetic field is not sufficiently.

For the long-distance Earth environment the following algorithm of the **corrected co-ordinates** calculation proposed by *V. Sergeev and N. Thsyganenko* [1980] is used:

- The magnetic field line tracing from the satellite position up to the Ionosphere (the stop trace altitude 110 km) using
**Main (dipole)**+**Extraterrestrial**magnetic field model (for example,*Tsyganenko [1987], or [1989], or [1990]*) - The
**CORLAT**,**CORLON**, and**CORMLT**of the original point are equal to the dipole latitude, longitude and local time of the produced footprint. - Corrected geomagnetic co-latitude is the difference: (90 deg - CORLAT).

*Hultquist, B. M, and G.Gustafsson,*On the magnetic time dependence of auroral zone currents,*J.Atmos. Terr., Phys.*, 19, 246, 1960.

Back to the description .- Stasiewicz K. Polar Cusp Topology and Position as a Function of Interplanetary Magnetic Field and Magnetic Activity: Comparison of a Model with Viking and other Observations, J. Geophys. Res., 96, 15789-15800, September 1, 1991.

Back to the description . - The main magnetic field
**IGRF**WWW site http://fdd.gsfc.nasa.gov/IGRF.html

Back to the description . - Sergeev, V.A., and Tsyganenko N.A. Magnetosphere of the Earth // M.: Nauka. 1980 (In Russian)

Back to the description . *Tsyganenko N.A.*, Global quantitative models of the geomagnetic field in the cislunar magnetosphere for different disturbance levels,*Planet. Space Sci.*, 35, 1347-1358, 1987.

Back to the description .- Tsyganenko N.A., Magnetospheric magnetic fields model with a warped tail current sheet. Planet. Space Sci. 1989. 37. 5-20.

Back to the description . - Tsyganenko N.A. Quantitative models of the magnetospheric magnetic field: Methods and results. Space Sci. 1990. Rev. 54. 75.

Back to the description .

*Dr. Victoria Prokhorenko**
Last modified 11 January 1999 *