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An optical study of multiple NEIAL events driven by low energy electron precipitation

By J.M. Sullivan, Michael Lockwood, B.S. Lanchester, E.P. Kontar, N. Ivchenko, H. Dahlgren and D.K. Whiter

Abstract

Optical data are compared with EISCAT radar observations\ud of multiple Naturally Enhanced Ion-Acoustic Line\ud (NEIAL) events in the dayside cusp. This study uses narrow\ud field of view cameras to observe small-scale, short-lived\ud auroral features. Using multiple-wavelength optical observations, a direct link between NEIAL occurrences and low energy (about 100 eV) optical emissions is shown. This is consistent with the Langmuir wave decay interpretation of NEIALs being driven by streams of low-energy electrons. Modelling work connected with this study shows that, for the measured ionospheric conditions and precipitation characteristics, growth of unstable Langmuir (electron plasma) waves can occur, which decay into ion-acoustic wave modes. The link with low energy optical emissions shown here, will enable future studies of the shape, extent, lifetime, grouping and motions of NEIALs

Publisher: Copernicus Publications
Year: 2008
OAI identifier: oai:centaur.reading.ac.uk:7509

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