uter
programs in FORTRAN. Those models were based on
Jacchia works (70 and 77) and their analytical versions,
since Jacchia assumed numeric integration of the diffusion equation in
order to compute density and composition as function of height. Numeric
integration normally demands computing time, and therefore analytical
means &#8220;fast&#8221;</span><span style="font-family: ms sans serif;"> in this
sense</span><span style="font-family: ms sans serif;">. All the models were recently converted to
C