Ionospheric Reflections from Heights Below the E Region

Abstract

SummaryThe pulse method of radio sounding has been used at 1· 75 Mc/s to detect low ionospheric regions whose voltage reflection coefficient exceeds 4 X 10-6 • Observations from February to July 1955 have revealed reflections, from 95 km vertical height and of day-time occurrence only, which are believed to originate in the lower E region. A region with a lower boundary predominantly at 85 km has been found to exist continuously, and previous suggestions as to its meteor origin are queried. A series of complex partial reflections have been detected during day-time only down to 53 km, with significant heights near 75, 67, and 55 km. The occurrence and strength of these lower reflections increases markedly during winter.From records of high absorption conditions during winter days, a connexion between the decrease in strength of E region reflections and the increase in strength of partial reflections between· 66 and 88 km approximately is demonstrated.

The effects of geomagnetic disturbances and atmospheric tides upon middle atmosphere winds and MF radar scatter at Saskatoon (52°N, 107°W, 61° geomagnetic)

“…Under these radar scatter upon earlier dynamic studies, including tides and conditions there is a high probability that a mean winds, and classifies summer as May-August wind value will result. 1987] has increased quite remarkable, consistent with the winter ionization in the D region associated with it anomaly affecting heights from 80 to 95 km most [e.g., Gregory and Manson, 1970], which may be severely. The effect of M and D events upon • due to changes in temperature, atmospheric is therefore less obvious in winter than in constitution, and dynamics.…”

Radio wave reflections from the mesophere: 1. Heights of occurrence

“…The conventional method of pulse sounding of the ionosphere is employed, with radiation at a fixed frequency of 1.75 Mc/s. The experimental arrangements, essentially those described previously by Gregory [1956], place emphasis on high sensitivity and good height resolution. At maximum sensitivity, the apparatus is capable of detecting a partial reflection and by Gregory [1956], information on the dy-whose equivalent voltage reflection coefficient namic processes is almost entirely lacking.…”

MF and HF radar techniques for investigating the dynamics and structure of the 50 to 110 km height region: a review

“…For example, Dieminger (1952), Gregory (1956Gregory ( , 1961, Titheridge (1962), Reid (1990), Jones et al (2004), and Hall et al (2006) discuss this for MF and HF, Bailey et al (1955) and Pineo (1956) for very high frequency (VHF; 30 to 300 MHz) forward scatter results, Bowles et al (1964) for both vertical and forward scatter VHF results, and Flock and Balsley (1967) for vertical incidence VHF results. At MF/HF, such preferred heights are subject to seasonal and annual variations, but persistent echoes occur from mean heights of about 65-68, 74-75, 83-85, and 92 km.…”

“…While the application of radars operating in the MF and HF bands to investigate the neutral upper atmosphere is one of the oldest such techniques still regularly in use, the techniques have been continuously improved, largely through the availability of better hardware (e.g., Reid et al 1995;Singer et al 2008;Li et al 2012) and readily available and economical but powerful computers, and provide a robust and reliable method of obtaining wind velocities (e.g., Stubbs 1973;Pancheva et al 2002), turbulence intensities (e.g., Hocking 1983;Holdsworth et al 2001), electron densities and collision frequencies (e.g., Thrane and Piggott 1966;von Biel 1977;Friedrich and Torkar 1983;Holdsworth et al 2002;Singer et al 2011), measurements of atmospheric structure (e.g., Gregory 1956;Hall 2000), temperatures (e.g., Tsutsumi et al 1999;Holdsworth et al 2006), and measurements of energy and momentum transfer (e.g., Reid and Vincent 1987;Murphy and Vincent 1993;Placke et al 2015) in the MLT region.…”