An apparent lifetime of auroral 630.0 nm (OI) emissions.

Abstract

An apparent lifetime of the auroral red line (630.0nm OI) emission was investigated by using monochromatic auroral TV images obtained on July 18, 1984, at Syowa Station, Antarctica. We tried to evaluate a mean energy of the incoming electrons by using the temporal variation of the red line intensity. The observed red line intensity is compared with a synthesized variation of the auroral red line solving differential equations for chemical reactions in the auroral ionosphere as well as the deactivation of excited state oxygen atoms. The observational results showed that the red line intensity changed gradually keeping an apparent lifetime of about 35-40sec while the green line intensity changed step-wise. The lifetime found is significantly smaller than a value (about 110sec) previously used for the interpretation of 630.0nm (OI) auroral emission. The comparison showed that the observed apparent lifetime is consistent with a synthesized aurora excited by a low energy electrons with a characteristic energy of 0.2-0.5keV. © 1992, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.