Influence of magnetospheric processes on winter HF radar spectra characteristics

Abstract

Abstract. This study investigates further the relationship between regions of the magnetosphere and the characteristics of HF radar Doppler spectra recorded in the ionospheric projection of those regions. It builds on earlier work, which has reported a relationship between the Doppler spectral width and the ionospheric projection of the magnetospheric cusp region, by introducing novel techniques for classifying the Doppler spectra recorded by the SuperDARN radars. We first review the geophysical factors that can condition the characteristics of the autocorrelation function (ACF) data produced by the radars. This leads to a classification scheme of the ACF data which is then applied to a large database compiled from winter data taken by the Northern Hemisphere Super-DARN radars. This statistical study shows that the ACF characteristics are not randomly distributed in space, but rather are spatially organized in the ionosphere. This paper suggests that these regions are ordered primarily by the low energy (≈ 1 keV) electron precipitation region and the presence of intense ULF wave activity.

Simultaneous optical, CUTLASS HF radar, and FAST spacecraft observations: signatures of boundary layer processes in the cusp

“…Combining PACE HF radar data and DMSP particle observations Baker et al (1995) found that broad multi-component Doppler spectra are characteristic for the coherent HF radar backscatter in the cusp. This has also been confirmed in statistical studies (André et al, 2002), and recently, Moen et al (2001) used HF backscatter to identify the cusp. The generating mechanisms for these decameter backscatter irregularities are, however, still open questions .…”

A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the morning sector ionosphere

“…The spatial distribution of these two classes of spectra in the polar ionospheres shows that they are not randomly distributed in space (Huber and Sofko, 2000;André et al, 2002). Significant spatial differences are also seen in the variation of the mean and median spectral width values with latitude and MLT , the preferred location for multi-component spectra matching the largest spectral width values.…”

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

“…The spatial organization of classes of backscatter spectra in the polar ionospheres (Huber and Sofko 2000;André et al 2002;Villain et al 2002;André and Dudok de Wit 2003) suggests that the origin of high spectral width values is related primarily to physical processes rather than instrumental and/or propagation effects. Suggested processes include the variability within the large-scale ionospheric convection pattern Villain et al 2002), smaller-scale vortical convection structures generated by filamentary FACs Huber and Sofko 2000), intense particle precipitation which can result in strong spatial and temporal non-uniformity in ionospheric irregularities, and low-frequency (*0.01-10 Hz) waves (André et al 1999(André et al , 2000Fig. 12 A statistical comparison of three ionospheric proxies for the OCB (see text for full details).…”