A COMPARISON OF THERMOSPHERIC [O] DERIVED AT EISCAT WITH [O] PREDICTED BY MSIS

In recent years aeronomic considerations of the value of the O+-O coll ision cross-section (Q(O+-O)) in the ionospheric F-region have resulte d in many values of a multiplicative adjustment factor (F) to the stan dard value of Q(O+-O) which had been in use from the mid sixties to th e late eighties. Q(O+-O) and oxygen concentration ([O]) appear as a pr oduct in aeronomic calculations, so F can also be considered a multipl icative factor for the oxygen. [O] derived at EISCAT for data from 198 4 to 1997 is compared to oxygen predicted by MSIS and values of F are calculated as a function of solar cycle and year. There is a solar cyc le variation, with F varying from .65 at solar minimum to 1.18 at sola r maximum. For solar fluxes between 100 and 160 solar flux units F at EISCAT is in good agreement with a value of F calculated for MSIS. No long term trend in the relationship between EISCAT [O] and MSIS [O] wa s found.