Some early observations of significant ionospheric modification resulting from F‐region heating by a very high power, high frequency transmitter located near Boulder, Colorado, are presented in this paper. A description of the Platteville heating transmitter facility, the locations of ionosonde and photometric diagnostic equipments, and the geometry of the experiment are given in a companion paper by Utlaut [1970]. A single‐plane inverted log periodic antenna, which has a half‐power beam‐width of the order of 90°, was used for transmitting. The ionosonde transmitter, which has a peak power of about 25 kw, was operated by using a 200‐Hz pulse repetition rate with a pulse duration of 64 μsec.
Any numerical method for inversion of the integral equation h'(f)= p.'(/N(z),f)dz must satisfy certain requirements in order to avoid introducing features into the true‐height profile which are not indicated by the ionogram. These requirements are first investigated by considering the equation as an integral transformation of fN(z) for several model distributions. In order to satisfy the above‐mentioned criteria a second‐order lamination process was developed; its mathematical principles are presented in this paper and its implementation at the Institute for Telecommunication Sciences and Aeronomy is discussed in the two following papers.
To be useful for studies of ionospheric processes, N(h) profiles must be obtainable from ionograms by methods that minimize uncertainties near the base and peak of the F region and that give the true shape of the profile with an accuracy commensurate with the available virtual height information. We present the principles of such a method, in which corrections are made for unobserved and ‘valley’ parts of the profile, and which gives a good convergence to the true curvature of the profile in each interval. Examples show a sequence of profiles calculated through the sunrise period at a midlatitude station. The E‐region valley is found to range between 40 and 150 km in width.
The analysis of digital ionograms taken in short‐time intervals shows rapid changes of sporadic E parameters. This is directly visible in the variation of the top frequency or maximum electron density of such layers. Angle of arrival data which were available with those ionograms also showed fast changes of the apparent direction and often large deviations from vertical propagation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.