Observation of a NEIAL event with a radar interferometer
(English)Manuscript (preprint) (Other academic)
We present the first measurements of Naturally Enhanced Ion Acoustic Line (NEIAL) echoes observed with 5 antennas. The observations were obtained with the European Incoherent CATter (EISCAT) radar and the EISCAT Aperture Synthesis Imaging receivers (EASI) installed at the EISCAT Svalbard site. Four baselines of the interferometer are used in the analysis. Based on the coherence estimates derived from the measurements we show that the enhanced backscattering region is limited in the plane perpendicular to the geomagnetic field. Previously it has been argued that the enhanced backscatter region is limited in size, however, here the first unambiguous observations are presented. The size of the enhanced backscatter region is determined to be less than 900500 m, and at times less than 160 m in the direction of the longest antenna separation, assuming the scattering region to have a Gaussian scattering cross section in the plane perpendicular to the geomagnetic field. Using aperture synthesis imaging methods volumetric images of the NEIAL echo are obtained showing the enhanced backscattering region to be aligned with the geomagnetic field. Although optical auroral emissions are observed outside the radar beam we show that the enhanced backscatter region and optical emission likely occur on the same geomagnetic field lines.
Auroral Ionosphere, Instability, NEAIL
Research subject Physics
IdentifiersURN: urn:nbn:se:kth:diva-159735OAI: oai:DiVA.org:kth-159735DiVA: diva2:787158
QC 201502102015-02-092015-02-092015-03-03Bibliographically approved