Observation of O⁺ (⁴P-⁴D⁰) lines in electron aurora over Svalbard

N. Ivchenko (1, 2) , M. H. Rees (1) , B. S. Lanchester (1) , D. Lummerzheim (3) , M. Galand (4) , K. Throp (1) , I. Furniss (5)

1 School of Physics and Astronomy [Nottingham]
2 Alfven Laboratory
3 Geophysical Institute
4 CSP - Center for Space Physics [Boston]
5 Atmospheric Physics Laboratory [UCL London]

This work reports on observations of O⁺ lines in aurora over Svalbard, Norway. The Spectrographic Imaging Facility measures auroral spectra in three wavelength intervals (H_?, N⁺₂ 1N(0,2) and N⁺₂ 1N(1,3)). The oxygen ion multiplet (4639-4696Å) is blended with the band. It is found that in electron aurora, the brightness of this multiplet, is on average, about 0.1 of the total brightness. A joint optical and incoherent scatter radar study of an electron aurora event shows that the ratio is enhanced when the ionisation in the upper E-layer (140-190km) is significant with respect to the E-layer peak below 130km. Rayed arcs were observed on one such occasion, whereas on other occasions the auroral intensity was below the threshold of the imager. A one-dimensional electron transport model is used to estimate the cross section for production of the multiplet in electron collisions, yielding 0.18x10^-18cm².

Domaines: Océan, Atmosphère; Sciences de la Terre

N. Ivchenko, M. H. Rees, B. S. Lanchester, D. Lummerzheim, M. Galand, et al.. Observation of O⁺ (⁴P-⁴D⁰) lines in electron aurora over Svalbard. Annales Geophysicae, 2004, 22 (8), pp.2805-2817. ⟨hal-00317574⟩