Observation of O<sup>+</sup> (<sup>4</sup>P-<sup>4</sup>D<sup>0</sup>) lines in electron aurora over Svalbard

Abstract

Abstract. 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 β , N (1,3) band. It is found that in electron aurora, the brightness of this multiplet, is on average, about 0.1 of the N + 2 1N(0,2) 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 (140-190 km) is significant with respect to the E-layer peak below 130 km. 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 0.18×10 −18 cm 2 .

Multispectral observations of auroral rays and curls

“…This supports an earlier finding [Ivchenko et al, 2004] that oxygen ion lines are enhanced in rayed aurora. The [OII] emission is strong in rays but absent in curls.…”

Observation of O+ 4P‐4D0 lines in proton aurora over Svalbard

“…[4] The Spectrographic Imaging Facility (SIF) is a suite of optical instruments, located at the auroral station (78.2°N, 15.8°E) near Longyearbyen, Svalbard. A description of the SIF is given by McWhirter et al [2003], and data reduction techniques are described by Ivchenko et al [2004]. Here we use data from the High Throughput Imaging Echelle Spectrograph (HiTIES) [Chakrabarti et al, 2001].…”

“…For N 2 + 1N(0,2) integration over the observed spectral range yields about 10 R, which is an underestimate, since part of the R branch extends further into the blue. Using the method described by Ivchenko et al [2004] we obtain 13 R for the 1N(0,2). Table 1 lists this value together with the observed brightnesses of O + 4 P-4 D 0 multiplet and H b , 11.9 R and 102 R respectively.…”

“…[8] Ivchenko et al [2004] found that the O + 4 P-4 D 0 brightness in electron aurora is on average 0.1 of N 2 + 1N(0,2). Modelling showed that the maximum ratio of the emissions does not exceed 0.5, a value only reached for electrons with energies of several 100 eV.…”

“…[11] We model the contribution from the electron precipitation using a transport model by Lummerzheim and Lilensten [1994], and the O + emission cross sections from Ivchenko et al [2004]. The modelled brightnesses are summarized in Table 1.…”