Abstract
Aspect angle dependence of the E region irregularity velocity at large flow angles
Department of Physics, La Trobe University, Bundoora, Melbourne, Victoria, Australia
Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
Department of Communication Systems, Lancaster University, Lancaster, UK
Space Research Unit, Finnish Meteorological Institute, Helsinki, Finland
Department of Communication Systems, Lancaster University, Lancaster, UK
Department of Physics, La Trobe University, Bundoora, Melbourne, Victoria, Australia
We present the Doppler velocity observations of 1-m plasma waves in the auroral E region by the Scandinavian Twin Auroral Radar Experiment (STARE) Norway VHF coherent radar in the context of simultaneous
and coincident measurements of electron and ion drift velocities determined by the European Incoherent Scatter (EISCAT) tristatic
radar facility. The measurements were performed in the afternoon sector (1500–2000 MLT) at seven locations along the STARE
radar beam 2 with different values of the magnetic off-perpendicular (aspect) angle α between 0.48° and 2.63° and at large angles with respect to the electron background drift (
= 55°–90°). It is demonstrated that the STARE line-of-sight velocity, normalized to the EISCAT-derived electron drift speed
at large flow angles, exhibits a decrease with increasing aspect angle, and the rate of decrease is investigated as a function
of the flow angle. We also compare the STARE velocity with the electron and ion drift velocity components along the STARE
radar beam look direction and show that, at large aspect angles, the E region velocity is correlated (anticorrelated) with the ion (electron) drift velocity component. The results are discussed
in the contexts of the linear fluid theory of the modified two-stream plasma instability and the theory of anomalous collisions.
Received 12 February 2007; accepted 13 July 2007; published 13 November 2007.
Citation: (2007), Aspect angle dependence of the E region irregularity velocity at large flow angles, J. Geophys. Res., 112, A11303, doi:10.1029/2007JA012342.
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