Simultaneous imaging of aurora on small scale in OI (777.4 nm) and N(2)1P to estimate energy and flux of precipitation
2009 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 7, 2881-2891 p.Article in journal (Refereed) Published
Simultaneous images of the aurora in three emissions, N(2)1P (673.0 nm), OII (732.0 nm) and OI (777.4 nm), have been analysed; the ratio of atomic oxygen to molecular nitrogen has been used to provide estimates of the changes in energy and flux of precipitation within scale sizes of 100 m, and with temporal resolution of 32 frames per second. The choice of filters for the imagers is discussed, with particular emphasis on the choice of the atomic oxygen line at 777.4 nm as one of the three emissions measured. The optical measurements have been combined with radar measurements and compared with the results of an auroral model, hence showing that the ratio of emission rates OI/N2 can be used to estimate the energy within the smallest auroral structures. In the event chosen, measurements were made from mainland Norway, near Tromso, (69.6 N, 19.2 E). The peak energies of precipitation were between 1-15 keV. In a narrow curling arc, it was found that the arc filaments resulted from energies in excess of 10 keV and fluxes of approximately 7mW/m(2). These filaments of the order of 100 m in width were embedded in a region of lower energies (about 5-10 keV) and fluxes of about 3 mW/m(2). The modelling results show that the method promises to be most powerful for detecting low energy precipitation, more prevalent at the higher latitudes of Svalbard where the multispectral imager, known as ASK, is now installed.
Place, publisher, year, edition, pages
2009. Vol. 27, no 7, 2881-2891 p.
Ionosphere, Auroral ionosphere, Particle precipitation, Instruments and, techniques, electron-impact, cross-sections, atomic oxygen, excitation, emission
IdentifiersURN: urn:nbn:se:kth:diva-18655ISI: 000268622700024ScopusID: 2-s2.0-75149181782OAI: oai:DiVA.org:kth-18655DiVA: diva2:336702
QC 201005252010-08-052010-08-05Bibliographically approved