Energy parameters of the incident auroral electrons derived by the intensity ratio of auroral emissions

Abstract

Average energy and total energy flux of the incident electrons in active auroras are estimated by using the intensity ratio of auroral emissions measured with a multi-channel photometer at Syowa Station, Antarctica, in 1990. To avoid possible ambiguities which are mainly caused by quenching effects on meta-stable species and complex excitation processes, we used intensity ratios of the emissions of allowed transitions such as 844.6nm (OI), 670.5nm (N_21PG), and 427.8nm (N_2^+1NG). Measured intensity ratios were directly compared with a result of model calculation of auroral emissions. The estimated energy parameters in active auroras showed a rapid change of average energy as well as total energy flux of electrons associated with pulsating auroras and intense auroral arcs. Average energy and total energy flux of the auroral electrons determined by the present method were consistent with the result of the previous in-situ observations of precipitating electrons. Our data analyses on active arcs in break-up phase showed that usage of the 427.8nm emission has difficulty due to a scattering effect of the atmosphere. Usage of 670.5nm emission in place of 427.8nm made it possible to evaluate the energy parameters of electrons even in the vicinity of intense auroral arcs.