Mixed-mode Oblique Ionograms: a Computer Ray-tracing Interpretation PDF Download

Author: James Robert Barnum
Publisher:
ISBN:
Category : Electronic data processing
Languages : en
Pages : 124

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Book Description
Twenty-four hour high-resolution FMCW soundings taken over an East-West 1900-km forward-propagation path show unexpectedly complex mode structure near sunset. Because of the presence of 1- and 2-hop sporadic-E modes, it was suggested that multiple reflections from sporadic-E and F-layers--such as 'M' and 'N' modes--accounted for much of the unexplained structure. This work represents an attempt to see how well these 'mixed' modes can be understood by employing computer ray-tracing procedures developed by Dr. T.A. Croft. A simple beta-Chapman layer, with its parameters adjusted to give synthetic ionograms that matched the experimental 1- and 2-hop F-layer modes, proved to be an adequate model for the F-layer profile over the path. Reference to the calibrated experimental ionograms yielded values for the sporadic-E reflection heights for each time of day. Assuming no horizontal tilts in layer density and ignoring the earth's magnetic field, synthetic ionograms involving multiple F-layer and sporadic-E reflections were then computed. The model-experiment comparisons show that surprisingly accurate estimations of both 1- and 2-hop and mixed modes are possible, using only relatively simple computational procedures. Although similar work has been done in this area, the present study is novel in its use of calibrated oblique ionograms for model derivation. The work should lead to a better understanding of both HF forward and backscatter propagation studies which are plagued with multiple, interlayer propagation modes. (Author).