This report is based on data obtained from one of 15 flights made by NASA in 1969 in the auroral oval with the instrumented Convair 990 aircraft. A two-channel interference filter photometer with passbands at 4260 and 4280 ¿ measured spectral changes in the intensity distribution of the N+2 first negative band at 4278 ¿. By using a model atmosphere and calculating the vertical distribution of energy deposition the characteristic energy was deduced from measured channel ratios. These results are compared with those obtained from the intensity ratio of the O I 6300-¿ and N+2 4278-¿ emissions. The values obtained by the two methods agree reasonably well as a whole. Differences that do appear may be attributed to departures from the simple one-parameter form of the electron energy spectrum. Time delays of a few seconds are observed between short-lived intensity peaks and the following rises in characteristic electron energy.