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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 1
Ann. Geophys., 23, 3–11, 2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Eleventh International EISCAT Workshop

Ann. Geophys., 23, 3–11, 2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Jan 2005

31 Jan 2005

Dynamic rayed aurora and enhanced ion-acoustic radar echoes

E. M. Blixt1, T. Grydeland1, N. Ivchenko2,3, T. Hagfors4, C. La Hoz5,1, B. S. Lanchester1, U. P. Løvhaug1, and T. S. Trondsen6 E. M. Blixt et al.
  • 1Dept. of Physics, University of Tromsø, N-9037 Tromsø, Norway
  • 2School of Physics and Astronomy, University of Southampton, UK
  • 3Alfvén Laboratory, KTH, Stockholm, Sweden
  • 4Max-Planck-Institut für Aeronomie, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
  • 5Cornell University, Earth and Atmospheric Science Department, Ithaca, USA
  • 6Institute for Space Research, Calgary, Alberta, Canada

Abstract. The generation mechanism for naturally enhanced ion-acoustic echoes is still debated. One important issue is how these enhancements are related to auroral activity. All events of enhanced ion-acoustic echoes observed simultaneously with the EISCAT Svalbard Radar (ESR) and with high-resolution narrow field-of-view auroral imagers have been collected and studied. Characteristic of all the events is the appearance of very dynamic rayed aurora, and some of the intrinsic features of these auroral displays are identified. Several of these identified features are directly related to the presence of low energy (10-100eV) precipitating electrons in addition to the higher energy population producing most of the associated light. The low energy contribution is vital for the formation of the enhanced ion-acoustic echoes. We argue that this type of aurora is sufficient for the generation of naturally enhanced ion-acoustic echoes. In one event two imagers were used to observe the auroral rays simultaneously, one from the radar site and one 7km away. The data from these imagers shows that the auroral rays and the strong backscattering filaments (where the enhanced echoes are produced) are located on the same field line, which is in contrast to earlier statements in the litterature that they should be separated.

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