Resumen de Estimating the peak auroral emission altitude from all-sky images

Luisa Sangalli, B. Gustavsson, N. Partamies, K. Kauristie

• The Magnetometers Ionospheric Radars All-sky Cameras Large Experiment (MIRACLE) network monitors auroral activity in the Fennoscandian sector of Europe. Some of the MIRACLE network stations include digital all-sky cameras (ASC, FoV 180o) that have been in operation since 1996. ASCs are geared towards morphologic studies of meso-scale (10-1000 km) aurora. The FoVs of the cameras overlap allowing optical triangulation and tomographic-like reconstruction of auroral features. The goal of this study is to evaluate the value of optical triangulation to estimate the altitude at which the peak auroral emission occurs using ASC images. The technique was tested for a thin stable auroral arc on November 22, 2000. The auroral arc was observed by ASCs located at the Abisko, Kilpisjärvi, Kevo and Muonio stations from 17: 32: 00 until 17: 38: 00 UT. The analysis presented in this paper deals only with the first pair of stations. The Auroral Image Data Analysis (AIDA) tools (a Matlab software package) was adapated for ASC geometry and used to triangulate the altitude of the auroral arc. Results showed that the peak emission altitude varied along the structure by about 40 km. Since the uncertainty for each measurement was at most 20 km, this variation along the auroral arc is physically significant. The average altitude (120-140 km) of the auroral stucture is in agreement with the altitude determined with the image matching method but it is greater than the most frequent altitude observed in prior studies (110 km).