HR: 1340h
AN: SA23A-0299    [Abstracts]
TI: A Technique to Separate Ground and Ionospheric HF Radar Backscatter for Ionospheric Remote Sensing
AU: * Blanchard, G
EM: gblanchard@selu.edu
AF: Southeastern Louisiana University, Department of Chemistry and Physics, Hammond, LA 70402-0878 United States
AU: Sundeen, S
EM: Stefan.Sundeen@selu.edu
AF: Southeastern Louisiana University, Department of Chemistry and Physics, Hammond, LA 70402-0878 United States
AU: Baker, K
EM: kbaker@selu.edu
AF: National Science Foundation, 4201 Wilson Blvd. Room 775, Arlington, VA 22230 United States
AB: The use of High Frequency (HF) radar for ionospheric remote sensing has recently proliferated, as in the case of the growing Super Dual Auroral Radar Network (SuperDARN). However, because of the complexity of ionospheric propagation modes and the fact that individual echoes of ground and ionospheric scatter origin may have similar spectral characteristics, it is often impossible to determine whether an echo is a legitimate ionospheric scatter echo or a spurious ground scatter echo. We have developed a technique that utilizes the statistical distribution of spectral parameters and range and elevation angle of arrival data of ground and ionospheric echoes to identify the origin of an echo with a high degree of confidence. For the two radar stations specifically presented here, the confidence of identification of an echo's origin is 90%. We use data from the Kapuskasing and Saskatoon HF radars for 12 days throughout the year of 2001 and examine the joint distribution of backscatter line-of-sight velocity v and spectral width w. We observe that for v >/= 100 m/s, which is presumably ionospheric scatter, the distribution of line-of-sight velocity decreases exponentially with v for a given value of spectral width. The e-folding velocity is 450 m/s. We extrapolate this distribution to smaller v to obtain the joint distribution of velocity and width in ionospheric scatter, which we subtract from the total distribution to obtain the distribution of velocity and width in ground scatter. These distributions, when normalized, intersect along the line v_[m/s] = 60 m/s - 0.4w_[m/s]. This line represents the separatrix between ground scatter and ionospheric scatter for these stations. To validate this separatrix, we investigate the distribution of the reflection heights calculated from echo range and elevation angle of arrival data. The distribution of reflection heights for presumed ionospheric and ground scatter are distinctly different and are consistent with the presumed identification. Finally, the separatrix provides a 90% confidence of identification of a particular echo as of ground scatter or ionospheric scatter origin based on the overlap between the respective distributions of spectral parameters. This result is robust, being independent of radar station and season. While the particular values of the separatrix parameters and confidence level may vary for other HF radar stations based on local ionospheric and surface conditions, the technique should be generally applicable.
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 2494 Instruments and techniques
DE: 6934 Ionospheric propagation (0689, 2487, 3285, 4275, 4455)
DE: 6969 Remote sensing
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005