Lecturer: Dr Hans Nilsson (IRF-Kiruna) Date: 2005-02-24 10:00 Place: Aniara
Incoherent scatter radar observations in the vicinity of dayside auroral arcs: the role of ionospheric feedback
A combination of EISCAT incoherent scatter radar measurements, optical and magnetometer data is used to study the plasma in and around pre-noon structured precipitation and auroral arcs. Particular attention is paid to regions of comparatively low E region density observed adjacent to arcs / structured precipitation in the EISCAT Svalbard radar field-aligned measurements. It is shown through comparison between luminosity and incoherent scatter electron density measurements that the low density regions occur primarily due to the absence of diffuse (CPS-like) precipitation rather than to any cavity formation process. Regions of high electric field and low luminosity / conductance are observed prior to intensification of the structured precipitation. The ionospheric current is enhanced in the low conductance region, indicating that the strong electric fields do not result only from ionospheric feedback, and thus are driven by magnetospheric processes. It is shown that this situation is favorable for an ionospheric feedback instability which can give rise to arcs and structured precipitation in response to the imposed enhanced electric field.
Created 2005-02-18 15:56:55 by Rick McGregor Last changed 2005-02-18 15:56:55 by Rick McGregor