Resolution No.4 (1973): Brightness of auroras

IAGA considering the progress in absolute auroral photometry and the theoretical understanding of the connection between N+2 IN band intensity and particle-energy input, recommends that in the future the brightness of auroras be reported whenever possible in terms of the intensity of the 4278 Angstrom N+2 band (preferably in conjunction with those of 5577 Angstrom and 6300 Angstrom [OI], 4861 Angstrom H-beta, and other features where appropriate). The use of International Brightness Coefficients should be strictly confined to the reporting of visual estimates.