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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 12
Ann. Geophys., 18, 1560–1575, 2000
© European Geosciences Union 2000
Ann. Geophys., 18, 1560–1575, 2000
© European Geosciences Union 2000

  31 Dec 2000

31 Dec 2000

On auroral dynamics observed by HF radar: 1. Equatorward edge of the afternoon-evening diffuse luminosity belt

M. Uspensky4,1, P. Eglitis2,1, H. Opgenoorth2,1, G. Starkov3, T. Pulkkinen1, and R. Pellinen1 M. Uspensky et al.
  • 1Finnish Meteorological Institute, Geophysical Research, PO Box 503, FIN-00101, Helsinki, Finland
  • 2Swedish Institute of Space Physics, PO Box 537, 751 21 Uppsala, Sweden
  • 3Polar Geophysical Institute, Apatity, Russia
  • 4Murmansk State Technical University, Sportivnaya 13, Murmansk, Russia

Abstract. Observations and modelling are presented which illustrate the ability of the Finland CUTLASS HF radar to monitor the afternoon-evening equatorward auroral boundary during weak geomagnetic activity. The subsequent substorm growth phase development was also observed in the late evening sector as a natural continuation of the preceding auroral oval dynamics. Over an 8 h period the CUTLASS Finland radar observed a narrow (in range) and persistent region of auroral F- and (later) E-layer echoes which gradually moved equatorward, consistent with the auroral oval diurnal rotation. This echo region corresponds to the subvisual equatorward edge of the diffuse luminosity belt (SEEL) and the ionospheric footprint of the inner boundary of the electron plasma sheet. The capability of the Finland CUTLASS radar to monitor the E-layer SEEL-echoes is a consequence of the nearly zero E-layer rectilinear aspect angles in a region 5–10° poleward of the radar site. The F-layer echoes are probably the boundary blob echoes. The UHF EISCAT radar was in operation and observed a similar subvisual auroral arc and an F-layer electron density enhancement when it appeared in its antenna beam.

Key words: Ionsophere (ionospheric irregularities) · Magnetospheric physics (auroral phenomena; magnetosphere–ionosphere interactions)

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