Research note Auroral O ＋ 732/733 nm emission and its relation to ion upflow

Abstract: Observations of auroral oxygen ion emission at 732/733 nm were made at the Aurora station in Longyearbyen (78.2°N, 16.3°E; λ m ＝ 74.9°) using an all-sky spec-trograph (ASG) during the winter season of 2000/2001. A statistical analysis showed that the highest occurrence of oxygen ion auroras at Longyearbyen was seen in the dayside of the 09–12 MLT region; the intensities of these auroras were also larger than those on the night side. To study the mechanism of ion upflow in the polar ionosphere, ASG data obtained on December 7, 2000, was analyzed together with simultaneous ionospheric data obtained by EISCAT Svalbard radar (ESR). Enhancements of electron temperature and ion upward velocity were associated with an increase in the auroral OII intensity at the magnetic zenith. This result suggests that an ambipolar electric field associated with elec-tron temperature enhancement caused by soft electron precipitation may be involved in the mechanisms that drive ionospheric ions upward. key words: aurora, oxygen ion, ion upflow, ES