Spectral Characteristics of Low-Latitude Auroras Observed from Japan on February 11, 1958 and on May 10, 1992.

Spectral characteristics of auroral displays seen from Japan are discussed.A spatially extended lowlatitude aurora of February 11, 1958, showed three spectroscopic components having different energy sources; (1) the "central part excitation" of the red doublet of [0I)6300 A and 6364 A, which is caused by low energy secondary electrons, (2) the "high-latitude auroral display" of [01]5577 A and N2' l N3914 A lines which is a counterpart of a typical high-latitude aurora, and (3) the "enhanced-airglow" of the N2*IN3914 A lines which is caused by the diffused energy loss process of precipitating energetic particles.A weak photographic auroral display which was observed in the northern region of Japan on May 10, 1992 also showed similar spectral characteristics to those of the extended event.This suggests that weak auroral events observed from Japan were produced by excitation due to low-energy electrons and the direct excitation due to incoming particles.