Mapping the outer LLBL with SuperDARN double-peaked spectra

Andreas Schiffler and George Sofko
Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, SK

Patrick T. Newell and Ray Greenwald
Johns Hopkins University Applied Physics Laboratory, Laurel, MD

Abstract

A SuperDARN HF radar pair (Saskatoon- Kapuskasing) has been used to measure Doppler spectra of backscatter from the dayside F-layer. Normally the spectra are single-peaked, but a small fraction exhibit a doublepeaked (D-P) signature. On the 2D convection maps, these D-P spectra occur in range cells located poleward of the convection reversal. A comparison with DMSP SSJ/4 particle data measurements and their mapping to magnetospheric boundaries shows that the D-P spectra are concentrated just equatorward of the magnetopause, in regions of spatially/temporally structured soft electron precipitation (about 300 eV) where the highly variable flux can reach 2- 5 ergs=cm2=s. The D-P spectra are most easily explained in terms of scattering from small-scale vortices of size less than the radar resolution of 45 km. The D-P spectral measurements are illustrated by SuperDARN and DMSP data for a dayside event on Feb. 20, 1995, when northward IMF conditions prevailed. We conclude that HF radar D-P observations can be used to map in real time the dayside 2D ionospheric footprint of the outer LLBL.

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• Diagram 3 (.eps)