Tuesday, 28 June 2011
Polarisation of the Auroral Red Line
Today we are looking at a paper that's just come out in Annales Geophysicae, which is entitled "Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments" (see full reference below). The auroral red line is very prominently visible in the photograph shown here.
Since controversial measurements published in 1959, "the polarisation of the thermospheric atomic oxygen red line at 630 nm has been ignored for almost fifty years until it has been recently re-investigated [...]. The red line emission at 630 nm is due to the transition between the O1D and O3P states with a corresponding energy threshold of 1.96 eV. In this study, the emission has been observed by a dedicated photo-polarimeter placed in the Svalbard archipelago" during five campaigns thus far. "[...] Polar observations are very difficult due to harsh weather conditions and instrumental problems, hence only few measurements have been possible." These experiments were supported by the EISCAT Svalbard Radar (ESR). The paper introduced here reports about the observations and puts them into the context of recent theoretical work on this penomenon.
Original article: Barthélémy, M., J. Lilensten, F. Pitout, C. Simon Wedlund, R. Thissen, D. Lorentzen, F. Sigernes, J. Moen, G. Gronoff, I. McCrea, H. Rothkael, H. Ménager, and A. Aruliah, Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments, Ann. Geophys., 29, 1101–1112, 2011 (link).
Photo: Very strong auroral emissions at 630 nm, pseudo-colour image by Thomas Ulich, intensity images from the all-sky camera of Sodankylä Geophysical Observatory (SGO).