|
|
 |
|
|
Ann. Geophys., 25, 675-687, 2007
www.ann-geophys.net/25/675/2007/
© European Geosciences Union 2007
Factors determining spectral width of HF echoes from high latitudes
P. V. Ponomarenko, C. L. Waters, and F. W. Menk
University of Newcastle, Callaghan, New South Wales, Australia
Abstract. Spectral width is one of the standard data types produced by the Super Dual
Auroral Radar Network (SuperDARN). A pronounced latitudinal gradient in
spectral width has been reported in the literature and is used as an
empirical proxy for the ionospheric footprint of the open-closed field-line
boundary. In this work we investigated the daytime radar echo properties near
the spectral width boundary using a multi-frequency sounding regime. We have
found that the relatively large spectral width values ≥150 m/s observed
poleward of the boundary are produced by ionospheric irregularities with
lifetime τl≃10–25 ms, which is essentially independent of the
scale size. These irregularities are statistically co-located with low-energy
(~100 eV) electron precipitation, which may play a major role in
producing F-region turbulence above 75 MLAT via restructuring the ionospheric
plasma on time scales ~τl.
Full Article in PDF (3624 KB) |
|
|
