IT is now well known that excess ionization associated with the aurora in or near the E-layer is capable of reflecting very high frequency radio waves with sufficient intensity to be easily detectable on a conventional radar display. Various estimates have been made of the height of the reflecting region, but these have all been obtained indirectly. Currie, Forsyth and Vawter1, using radars on two frequencies with different lobe-patterns, obtained a most probable height of 108 km. from histograms of echo ranges obtained over a long period. Dyce is quoted2 as making the assumption that an echo was most likely to be received if the ray from the radar were perpendicular to the Earth's magnetic field line at the echo point. By comparing the probability contours of echo occurrence with contours of various angles of incidence at the echo point, he found a height of about 80 km. for Alaskan observations and around 100 km. for those made at Ithaca. Bullough and Kaiser3 on one occasion, by assuming that an echoing region observed over a wide arc was at a constant height, estimated a figure of about 120 km.
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Currie, B. W., Forsyth, P. A., and Vawter, F. E., J. Geophys. Res., 58, 179 (1953).
Booker, H. G., Gartlein, C. W., and Nichols, B., J. Geophys. Res., 60, 1 (1955).
Bullough, K., and Kaiser, T. R., J. Atmos. Terr. Phys., 5, 189 (1954).
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UNWIN, R., GADSDEN, M. Determination of Auroral Height by Radar. Nature 180, 1469–1470 (1957). https://doi.org/10.1038/1801469a0
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