Polarization electric field and Farley-Buneman instability during a precipitation event.

• Published in: Journal of Atmospheric and Terrestrial Physics
• Main Author: del Pozo, C. F.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 1994
• Subjects: Farley; EISCAT
• Online Access: https://eprints.lancs.ac.uk/id/eprint/22672/; https://doi.org/10.1016/0021-9169(94)90200-3

An anomalous polarization electric field may be set-up in the lower auroral E-region in response to an electron precipitation event during unstable electrojet conditions. For instance, observations during post-midnight to early morning hours on 06–07 June 1990, using the EISCAT radar facility in Scandinavia, show that the in-situ dynamics of the E-region ionization may be radically affected by the presence of the Farley-Buneman instability. In this case, the measured ion drifts at 105 km height are exceptionally strong and comparable in magnitude with the E × B-drift in the F-region, mapped along the same magnetic fieldline. In this paper we present a model to explain the main features of these observations. We assume a simple relaxation model for the E-region ionization generated by an instantaneous electron precipitation event during diffuse aurora conditions and in the presence of the Farley-Buneman instability. In these conditions and for times smaller than the ionization lifetime (tens of seconds to a few minutes), the induced polarization electric field to restore charge quasi-neutrality may radically increase the ion drift velocity, and effectively decouple the ion motion from the dynamics of the neutral atmosphere.