Modelling and observations of the energy spectrum of precipitating electrons using joint EISCAT-ASK (Auroral Structure and Kinetics) measurements

Ashrafi, M.1, Lanchester, B.1, Whiter, D.1, Dahlgren, H.2 and Ivchenko, N.2

1 School of Physics and Astronomy, University of Southampton, UK
2 Space and Plasma Physics, School of Electrical Engineering, KTH, Stockholm, Sweden

A time-dependent ion chemistry model is used to derive the energy spectrum of precipitating electrons in dynamic structured aurora, using multi-spectral measurements from the ASK instrument combined with radar electron density profiles. During the winter season of 2006/7 the ASK instrument was deployed at the EISCAT Tromsų site. Events from 22 October 2006 with fast moving filamentary auroral structures on sub-kilometre, sub-second scales have been analysed in conjunction with EISCAT radar measurements, in particular the tristatic measurements of electric fields in the region of the dynamic aurora. These measurements are discussed in terms of the possible physical auroral acceleration mechanisms.

The ASK instrument consists of three narrow field of view imagers, each operating with a narrow passband filter to image auroral emissions in different spectral bands. Each camera has a 3 degree field of view centred on the magnetic zenith (corresponding to 5 km at 100 km altitude) and sub-second integration time. These features make ASK an ideal instrument for studying dynamic and structured aurora. The possible combinations of observed emissions (N2 1PG 6730, [OII] 7320, OI 7774) provide a unique dataset for optical studies of spectral ratios and variations in different auroral features.