ESA Science & Technology - Mapping of Cluster EDI measurements into ionosphere

Illustration of the mapping procedure. The measured convection velocity at the spacecraft position x^(m)₀ is converted into a spatial vector d^(m) by multiplying with a scaling factor.

The endpoints of this vector, x^(m)₀ and x^(m)₁ are then mapped along the magnetic field to 400 km altitude into the ionosphere, based upon the Tsyganenko T2001 model. 

Here the corresponding ionospheric convection velocity is obtained from the mapped vector d⁽ⁱ⁾. Since the magnetic field converges, the separation at 400 km, d⁽ⁱ⁾, is much smaller than d^(m).

The scales are exaggerated for clarity.