PARAMETERS OF THE O(S-1) EXCITATION PROCESS DEDUCED FROM PHOTOMETER MEASUREMENTS OF PULSATING AURORA

Intensity time-series of the 427.8 nm N-2(+)(1NG) (0,1) band and 557.7 nm O(S-1-D-1) line emissions were obtained with 0.05 s time resolutio n during intervals of pulsating aurora. Using an impulse response func tion analysis technique in conjunction with synthetic intensity time-s eries constructed using measured data, we estimate the influence of me asurement noise and a non-linear component of the covariance between t he 557.7 nm and 427.8 mm intensity time-series on the inferred paramet ers of an O(S-1) indirect excitation model. Non-linear effects had no additional influence beyond that of measurement noise on estimates of an indirect process. After accounting for the influence of measurement noise, indirect excitation accounts for between 30% and 100% of O(S-1 ) production, with an average for our measurements of 58%. The average effective lifetime of the species responsible for the indirect excita tion process is 0.13 s. The average percentage contribution from the i ndirect process is 14% lower, and the effective lifetime slightly long er, than values obtained when noise is not accounted for. Non-linearit ies between the auroral emissions limit the determination of the O(S-1 ) effective lifetime by this technique. We obtain an O(S-1) effective lifetime distribution with a mean of 0.71 s and a sharp cut-off at the radiative lifetime of similar to 0.80 s. O(S-1) state effective lifet imes decrease as average incident electron energies, determined from t he relative O(S-1-D-1) and N-2(+) (1NG) intensities, increase. Collisi onal deactivation of the O(S-1) slate can account for only of the orde r of 55% of the energy dependence of the O(S-1-D-1) and N-2(+)(1NG) in tensity ratio.