The aim of this paper is to show the gain of the global fit procedure
compared to the classical gate-by-gate analysis in the simultaneous de
termination of the temperatures and composition profiles in the lower
F region. A method for the evaluation of the transition altitude and t
he width of the transition region between molecular and atomic ions is
described in the case of the EISCAT CP1 experiment; it is validated u
sing a simulated experiment. It is shown that alternating-code gates h
ave to be processed together with the long-pulse gates. Our new method
is applied on six days of actual data. The results obtained during qu
iet periods are compared with independent estimations.