The applicability of fMIN-parameter for the study of radiowave absorption in the lower ionosphere

Ionospheric absorption data obtained at El Arenosillo by the A-3 Method have been correlated with fmin data of the same station and with data of Ebre Observatory to test the merit of this parameter for ionospheric absorption measurements. The fmin data of both stations have been compared also with each other in order to determine the "effective radio" of this parameter. The fmin data have been deduced from the vertical incidence sounding ionograms recorded in both stations with similar equipment, digisonde DGS-256. The results show that one has to be very cautious with the use of fmin for absorption studies. They also show that the fmin "effective radio" is less than it was thought.