On the absolute intensity of incoherent scatter echoes from the ionosphere

New observat ions h ave been made of the absolute intensity of in co herent seaLLe l' ec hoes from t he ionosphere, at a station ncar Lima, Peru . In order to analyze Lhese obse rvat ions properly, the paper begins wi t h a rederi vation of the radar equation in iLs form a ppropriate to in co herent scatter studies . The resul t of t hi s deri vation is tha t a correction factor of a pproximately 2 mu st bc appli ed to th radar equation in its form genera lly used in th is work. D etails given of t he observat ional parameters of the r adar sy. te m permit p rec ise compa riso n of t he present results with results of other worker. The observations indicate that t he average rad ar cross section per Fee electron is usua ll y c l o~e to the t heorctica ll y predicted valu e of one ha lf t he clas ical Thomson cross sec Lion. Thi s suggests that Lhe ionosphere is usua lly in a conditioll of thermal equilibrium beLween ion a nd e lectron s. Occasion ally , pa r t icula rl y a t sunrise, the observed cross section is s tilll o\\'er , approximatin g one quarter of t he classical Thomson cross section. Thi observation wou ld agree with Lhe theo retica l p red ic t ions of J . A. F eje r [19611 if the electron te mperature at sunri e in t he F r egion exceeds Lhe ion temperature.