Auroral images and particle precipitations observed by the sounding rocket experiment at Syowa Station

摘要

Three sounding rockets were launched in 1984 from Syowa Station in Antarctica into different types of aurora, designated as AURORA I (an active auroral arc at the substorm expansion phase), II (a stable arc prior to the substorm onset) and III (a diffuse aurora during the recovery phase). A new low-light-level television camera was also used to take an auroral picture downwards from the spinning rocket, together with the electrostatic quadrispherical and magnetic electron spectrometers to measure the energy spectrum of auroral particles (electrons). AURORA I showed greater values in both auroral emission and electron density than for AURORA II. AURORA III, although the auroral emission intensity was much less of course in comparison with AURORA I, the electron density showed a pronounced enhancement in the D region and was comparable with the case of AURORA I above the E region. The electron temperature for the three cases do not differ so much and are quite similar with one another below 150km in altitude. As for an energy spectrum of auroral electrons, AURORA I and II showed an inverted-V type monoenergetic peak with much greater energy for AURORA I than for AURORA II, whereas AURORA III exhibits a power-law spectrum with a small superposing monoenergetic peak around 0.5keV above 200km in altitude. A differential energy flux of trapped electrons is generally greater than that of precipitating electrons. The television camera data taken from the rocket showed a dependence of auroral color spectrum on the auroral activity, i.e., the ratio of an apparent emission rate at 427.8nm and an illuminance in a visible range (400 to 800nm) becomes greater for brighter aurora.